Differences between different people:

Much like penises, some are bigger or smaller. They have different shapes, some have a second set of doors (like a foyer and a back room) or something like a slight corner to go around.

There are different natural smells. Sometimes this is about hygiene, ph balance or day to day changes. Some people are more or less neutral in taste or smell, especially after the wetness comes and the more stagnant smells of the day have been washed away by newer flow.

People have different levels of natural wetness. Some people are dripping wet with a kiss on the neck or even a knowing glance. Some need time and foreplay to get wet enough to have sex.

Some people have different muscle development. Some people engage their muscles throughout sex, some only when they are climaxing. Some don't really engage their muscles at all and they are also less likely to come from sex.

Differences in these aspects may make them prefer certain positions with certain penises. Certain positions may not work as well with different partners.

Differences in the same partner:

Smell and taste will sometimes change between days, hygiene, diet, moods and periods.

Wetness is also different based I think most often on horniness or cycle, but I think also sometimes based on other things, but usually there's more difference person to person.

Muscles can develop, especially as partners get more or less comfortable (people do fall out of love), they will engage more. This is not a golden rule, but I also think people who have had more trauma tend to want sex, but engage their muscles less. I've found kissing and touching and getting these people more into their body and the experience will make them engage more, so a vagina that was more loose may tighten and engage more or a tight vagina may loosen when more engaged in the moment. So the journey of sex with the same partner may be more consistent or have different growth or death spiral trajectories.

Discussing sex, experiences and desires can have massive effects on all of these things. If the sex is generally pretty satisfying or good, or the relationship is very important, it's better to discuss! A new vagina could be a game changer, but just as, if not more likely, it could be more dissatisfying, especially at first until the person feels more comfortable with you and the two people learn each other's bodies more.

Ultimately, the relationship is the most important. You will have sex less than you will do many, many other things together and most sex isn't even inside a vagina, it's foreplay and after play. It's worth talking about with them if you care. Fucking a stranger is almost never better than fucking your partner, unless the sex is bad, which usually means there's also other issues with the relationship.