I like small bags, especially for evening. It forces you to edit down to the most important things. Most of all, you and your clothing can be appreciated and it is very feminine I have 25cm Birkin and 28cm Kelly and they are great Anyone agree with me? ... Or not
I like all sizes inclusing the smaller ones. Gracekelly, one reason I purchased my 28 cm Kelly was to keep my contents on the downside. I also feel that the 28 cm carries much more easily into evening. The 30 cm and above still look good, but if you are more petite and short like I am I thought the 28 cm worked the best. (for the day to eve transition) Again, it is one of those preference things.
However, when I want to be a bit more radical I do pull out the large bags and they look great as well.