There is a huge difference between 18/19 and 24! I remember as a grad student how ready I was to move off campus and into a real apartment and start becoming a grownup. So your thought process is spot on and you have the advantage of figuring out this difference well before moving here.
You don’t mention what your major is going to be but that has to be taken into account, of course. Both schools have outstanding reputations in many areas.
Pratt will have lots of older students at the Brooklyn campus as both undergrads and grads. My D1 is a 19 year old foundation student and one of her best friends is a mid-20’s gal from France who is an accomplished artist in her own right but feels it’s time to get that college degree. Some of the Pratt grad programs are in Manhattan (graphic design, for instance) but others are on the Brooklyn campus. Pratt is not going to be a “typical” college by any means because it attracts very un-typical students of all ages.
On the other hand, nothing says adventure like living right in Manhattan itself. It’s the #1 great town here in the USA.
Clinton Hill, Williamsburg, etc. is a lively residential part of Brooklyn filled with young professionals, NYU students, Pratt students, etc. It’s an artsy area with lots of fun restaurants and night spots. It’s also incredibly ethnically and culturally diverse. While urban, it’s quieter than the noisy bustle of Manhattan. Many students at both schools are going to commute (from Brooklyn to Manhattan, for instance). I’d say that if you like to get out and have a great time, then be able to retreat to peace and quiet, Brooklyn would be a better choice. The Pratt campus has the advantage of being a real campus so you aren’t dragging your art work around town - it’s a beautiful green space in the midst of the most densely packed urban area in America, which is a significant attribute.
If you are just beginning studio in the BFA program then you’ll need to do your foundation year with a lot of 18/19 year olds, regardless of which school you attend. However, as a transfer student you are going to be encountering - and dorming with - other transfer students who are naturally going to be older. Among the undergrad population, SVA is divided pretty equally among in-state, out-of-state, and international. Pratt has about 50% from out-of-state, and a little more than a quarter of it’s undergrad population from international (the rest, about 22%, from NY). So both are pretty diverse that way.
So it really comes down to what you are looking for, which school seems to be the better fit in terms of meeting your needs, and which is a better fit financially (not just in terms of scholarship but in terms of housing rates which might be very different between the two schools. Brooklyn housing tends to be less expensive than Manhattan’s). You can also transfer from one to the other if your first choice doesn’t work; however, you’ll need to check to see what the policy about retaining that scholarship would be if you didn’t accept this year (but transferred later on).