If the pill and liquid both contain the same amount of the same ingredients, the effects are essentially identical.
Generally speaking, liquids are absorbed and metabolized more rapidly, while pills are absorbed more gradually and stay around longer. Simply put, liquids are immediately effective, while pills are persistently active.
In addition to improving your basic dietary balance, use these pills and liquids wisely. One option is to take pills daily and use drinks for their added refreshment. Moreover, whatever form you take, be careful not to exceed the tolerable upper intake level.
Reference: New Vitaminology by Yoshinori Itokawa (Footwork Publishing), et al.

There are several factors that affect the absorption rate of vitamins, so there is no comprehensive consensus on what percentage is absorbed. The following factors affect the absorption rate of vitamins.

Reference: Vitamin Handbook

In Japan, vitamins in pill or capsule form used to be treated as medicines, but since the loosening of regulations in the 1990s, they can now be treated as foods.

The main vitamins associated with metabolizing fat are vitamin B₂, niacin, and pantothenic acid. These vitamins are coenzymes of the enzymes necessary for metabolizing fats, so when there is a lack of them, metabolism may be impaired. A lack of vitamin B₂ in particular halts the metabolism of fatty acids and their use as energy. While there are many vitamins associated with the metabolism of fatty acids, this is the reason only vitamin B₂ is called the "fat metabolism vitamin." The above vitamins, as well as vitamin B₁, are also involved in the breakdown of carbohydrates.

For those who wish to increase fat metabolism, in addition to exercise and diet, it is important to replenish B-complex vitamins.

Vitamins contribute to metabolic processes throughout the body. A lack of them can manifest as a deficiency, but in many cases, it manifests through changes in the skin and mucous membranes. The following are examples of the links between vitamins and the skin and mucous membranes.

For foods with nutrient function claims, the nutrients which in Japan are permitted to be labeled "This nutrient helps maintain the health of skin and mucous membranes" are vitamin A, beta carotene, vitamins B₁, B₂, and B₆; vitamin C, niacin, pantothenic acid, biotin, and zinc.

Reference: Dictionary of Vitamins. ed. The Vitamin Society of Japan, et al.

While vitamins and minerals are essential at every stage of life, according to the Dietary Reference Intakes for Japan (2020 edition), pregnant women are recommended to increase their intake of vitamins and minerals such as vitamin A, vitamin D, folic acid, and iron in comparison to women who are not pregnant.

Vitamin D is necessary for the formation of bones, so the intake guidelines for pregnant and nursing women are set higher. Folic acid is a necessary nutrient for cell division and DNA replication, and it is known that taking an additional 400μg of folic acid daily from 4 weeks before conception to the 12th week of pregnancy in particular reduces the occurrence of neural tube disorders.
Conversely, while there are no vitamins pregnant women should avoid, there are some vitamins which can cause problems if you take too much. Toxicity specific to pregnant women has been reported for vitamin A, and there are reports that fetal abnormalities have been observed in cases in which 10,000IU (3,000μgRE) were taken daily over an extended time period.
The American Council for Responsible Nutrition (CRN) has stated that side-effects do not occur for doses of 10,000IU (3,000μgRE) and below, but in Japan, making a more conservative estimate for the sake of safety, the safe amount which will not produce negative health effects in almost all people is set at 9,000IU (2,700μgRE). As it is an important vitamin that is essential for growth, it is best to take some vitamin A in the form of beta carotene, which does not have any risk of overdose.

Finally, a woman's nutritional status may worsen during pregnancy due to changes in the sense of taste or reduced dietary intake caused by morning sickness, etc. The most important point is to get three balanced meals, but using supplements to compensate for nutrients that tend to be lacking is another available option.

Not all nutrients humans need can be produced in the body. Consequently, we replenish our supply of water and nutrients, etc. every day. Supplements differ in that they supply only the components of food, come in pill or capsule form, and are not satisfying in the sense of taste, but they are the same in the sense that they supply nutrients.
Generally speaking, as the Ministry of Agriculture, Forestry and Fisheries (Japan) advocates, "The foundation of a healthy diet is a main dish, a main vegetable, and side dishes," so you should try to prepare balanced meals. However, getting only specific nutrients from foods, such as getting all the vitamins you need from normal meals when trying to lose weight, or smokers taking more vitamin C, which they tend to lack, can be extremely difficult. In such cases, taking vitamins as a supplement is thought to be beneficial.

The vitamins in foods and the vitamins taken as supplements are absorbed and metabolized by the body in essentially the same way, so it is believed that taking supplements does not change the way in which vitamins originating from foods are used.
As for the frequency of intake, to maintain a constant state of saturation of vitamins in the body and be prepared for expending a large amount of vitamins through exercise or stress, it is recommended that you proactively get vitamins from food and supplements daily, and not only when fatigued.
For reference, the maximum tolerable intake for vitamins and minerals, etc. which carry a risk of negative effects from excessive intake are established by the Dietary Reference Intake for Japanese. These amounts have been determined to be safe for daily intake. Generally speaking, as long as the amount is within the daily recommended intake listed on product labels, there should be nothing to worry about.
(Response from Dr. Osamu Igarashi, Professor Emeritus, Ochanomizu University)

Here are three representative examples of synergistic and additive effects.
The B-complex vitamins include vitamin B₁, B₂, niacin, pantothenic acid, and biotin, and they are involved in each step of the metabolism of carbohydrates. Accordingly, if you lack even one of them, your body will become unable to metabolize carbohydrates properly.
Among B-complex vitamins, folic acid and vitamins B₆ and B₁₂ are known to be involved in the metabolism of homocysteine. High levels of homocysteine are said to increase the risk of stroke and heart attack. Patients with high levels of homocysteine in their blood were administered folic acid and vitamin B₆ and B₁₂, both alone and in combination, and it was reported that homocysteine levels were reduced more when vitamins were administered in combination than when administered alone. Beta carotene, vitamin C, and vitamin E all function as antioxidants, and have been administered in combination in various clinical trials. Among them, vitamin C is known to reactivate the antioxidant action of vitamin E that had become inactive.

Reference: Know Your Vitamins by Toshikazu Yoshikawa (Shufunotomo Co., Ltd.)
Vitamins by Osamu Igarashi (Maruzen Library)

There have been many reports of vitamin deficiencies caused by medications, so we will focus on medications frequently carried by pharmacies, and present a number of cases where you should be careful. Please contact a specialist such as a doctor or pharmacist for detailed information.
Additionally, among over-the-counter medicines, vitamin B₁₂, folic acid, and iron deficiencies have been reported for H₂ receptor antagonists, medications for stomachaches and heartburn. One of the symptoms of these deficiencies is anemia.
Avmard J P et al; Haematological adverse effects of histamine H₂ receptor antagonists.; Med Toxicol&Adverse Drug 3(6), 430-, 1988
Itokawa Y. The interaction of Vitamins and drugs. Prog Med 5, 623-. 1985.

The following are examples for other prescription drugs.

Harm from smoking affects not only smokers themselves, but also the non-smokers around them. This is because tobacco smoke, particularly secondhand smoke, contains carcinogens and many other harmful substances.
In comparison to non-smokers, it is known that smokers metabolize vitamin C more rapidly in order to counteract the harmful substances that are inhaled, reducing the overall amount of vitamin C in the body. It is also said to reduce the absorption of vitamin C in the small intestine.
Accordingly, to protect your body against harm from smoking, it is recommended that you take sufficient amounts of antioxidant vitamins such as vitamin C, vitamin E, and beta carotene.
(Reference: New Vitamin C and Health, Vitamin Mineral Book)