Hybrid bike size issue.. help?
Smaller bikes are easier to ride and you can raise the saddle to the correct height so your knees aren't damaged. If you go too small you can get toe overlap with the front wheel, but on a mountain bike the wheelbase is longer and this is unlikely to be an issue.

Generally women have shorter torsos and longer legs. So they difference in a women's frame is generally a shorter top tube. Getting a smaller size frame and raising the saddle a few extra cm's will do the same thing to a man's bike.

Please don't get a man's bike that is too big for you, it's never going to be fun to ride.  If you have the opportunity to ride both sizes, take it and you'll see what I mean immediately.

I ride over 8000k's per year and the only times I've felt uncomfortable was on a frame that was too large by a cm or so. Couldn't get rid of them soon enough.