I started off with USCGA as my first choice (different time, of course). I ended up at USNA. Below were the factors for ME. YMMV - and, times have changed making some of the below OBE (overtaken by events).
I went to a really, really small h.s. (60 per class). When I visited USCGA, it felt like h.s. in that I was constantly seeing the same people over and over again -- and that was in a long WE. I wanted a college where I didn't know everyone.
AT THE TIME, USCGA was under the Dept. of Transportation whereas USNA was under DOD. When Reagan came in as President in 1981, he increased DOD funding and cut almost everything else. Thus, USCGA lost its band and other stuff just at the time I was about to enter.
The women's uniforms AT THE TIME looked like flight attendants, complete with red scarf. Not kidding.
I'm not a fan of New England or their winters.
AT THE TIME, there were a lot more opportunities for women in the USCG than the USN and I thought their missions were really interesting! However, primarily the first item above is what motivated me to choose USNA. I must confess that there were times (during the days when opportunities for women in the USN were very limited) that I somewhat regretted my decision.
I would say your decision should be partly the SA and partly the service. I say this b/c, for those who don't stay past their commitment, the time period is roughly the same (4 vs. 5 years). Does a smaller environment appeal to you? (For example, if you attend a h.s. where there are 1000 students per class, you might really appreciate a smaller "college"). Do you want to do drug interdiction, ice-breaking, SAR, etc.? Do you want earlier chance for command -- of smaller ships and facilities? Do you want the option to go USMC? Do you want to be a nuke?
Both are absolutely terrific schools. I've had more than a few candidates turn down USNA for USCGA and been very happy. So, great choice to have!