I'm 6 feet tall and don't have a 25 (yet). However, I found that in terms of practicality sizes like 30 and 35 are best, but as others pointed out it also comes down to preference, what you carry and so on... Personally I'm going for a 25 because I want a Birkin that holds my essentials yet is not overwhelming and small enough to be a dinner bag, after work drinks kinda bag and also as away to intruduce color to my relatively neutral handbag "collection".
Added: Even though I'm on the taller side, I do not factory height into my decision making as my height has nothing to do with my needs and I'll put my needs before "proportions".