I like both schools but the biggest difference for me is the Dartmouth community. Its much more campus based with a tighter knit student body. Dartmouth also has an incredibly amazing undergraduate experience with lots of grants, sophomore summer, the best study abroad in the country (for majors AND languages), and tons of awesome traditions and big weekends. The outdoors are also a plus. D has its own ski mountain, the river to swim in during the summers, and lots of natural beauty.
As an adult, my impression is that Dartmouth students are really nice kids who happen to be brilliant. Whether that is good for you is not for me to assume. I do, however, think that the campus cultures are quite different, so different that if you visit both schools, you will know.
I've heard that Georgetown's campus is not very attractive.. obviously it's got great academics and EC's but if you are looking for a beautiful campus in the middle of the wilderness, with tons of outdoor opportunities PLUS great academics and EC's, then definitely go for Dartmouth.
If you were admitted to Dartmouth ED, then this question would be a moot point.
If you have already been accepted to Gtown EA- (meaning that you would have to apply to Dartmouth RD)congratulations, it is a wonderful school.
If you have not been accepted to Gtown, then I think that you should wait until you either have a likely letter or RD admissions from either/both schools in your hand before deciding "where you think you should attend" and "why someone should convince you to come" as you may find that the decision (s) may end up being made for you.
I am not doubting the veracity of your statement, however, do you have an actual likely letter from Maria Lakaris?
Although you may be a recruited athlete and your prospective coach may be highly supporting you, you need a green light from admission in the form of a likely letter.
both are terrific schools ... and I'd think the demogrpahics (race, affluence, % of prep school students, scores, etc) are pretty similar. The locations are both very strong points for the schools ... and VERY different ... Georgetown is in a terrific urban environment ... while Dartmouth has one of the classic college town experiences. I would think if you visit both one of the locations will jump out as a better fit for you.
My son (coincidentally also a tennis player) had the same fortunate dilemma 3 years ago when he was accepted into Georgetown SFS and Dartmouth. As a very politically active kid, he was initially very torn and confused. All it took was 24 hours at Dimensions, the April weekend for admitted students, and Georgetown was no more. He has never regretted one moment of that decision.
My sister was admitted into both schools (as well as a few other Ivys) but narrowed it down to Dartmouth and Gtown. When she went to visit Dartmouth for a fortnight, she found that ALL they did was drink. She left after the first night and never looked back. She graduated from Gtown (SFS) and is now in the middle of her PH.D. program. Although Dartmouth is an "IVY," that should not be what drives your decision. Go and stay on both campuses and see which one is more of a fit for your personality. Dartmouth is in the middle of nowhere land while Gtown has so much to offer in terms of culture, intern opportunities, etc.