I looked at both with my D (she ended up choosing another excellent LAC in PA) and we liked the two colleges very much. She is a science person and gave an edge to F&M because she felt they were a bit better in her area of interest. In general she felt that F&M was a bit preppier and she liked the campus (although we were there on a very rainy day) while Dickinson seemed to stress a “global education” including travel abroad. And it sounds silly but she didn’t like the road that went through Dickinson’s campus – but that really is a terribly minor thing.
Overall they are two great schools and you can’t possibly made a bad choice. She has acquaintances from HS who are Dickinson and F&M and they are all very happy at their respective college. I’d wait and 1) see where you get in 2) see how the finances turn out and 3) try to re-visit each school (my D was able to shadow a student for a day/attend classes at her top two LAC choices) before deciding.