This is the never ending question. That is how I found this forum too! I went back and forth trying to decide for months and then finally decided on the 25. I think it depends on how much you carry and how much of a "big bag" person you are. The 30 is just enormous to me - although I do like how it looks on others. I can fit a ton in my 25 and yes, the opening is a little narrow but I don't have any problems with it. To me it is the perect size. I carry a good size wallet, agenda, makeup bag, lots of key, cell phone and on any given day there are also toys in it for my kids. I have no regrets getting the 25. Good luck!