DH is pushing for a 25 cm, but…

Your DH likes the woman in his life to be feminine and what is more feminine than a 25 sellier kelly.... Tell him you can be very feminine with a 28cm kelly too (and practical)... and VERY VERY feminine if the kelly was say in Porosus croc....
 
Kittenhead, how tall are you? Maybe your DH thinks the 25cm is more in proportion? I like the 25cm much better on myself (I'm about 4'10") than the 28cm. I have 25cm Kellys in both sellier and retourne and they both can hold everything I need to carry around. But, I would definitely hold out for black box over chocolate epsom. Every gal needs a great black box Kelly!

Either way, though, your DH sounds like a peach!
 
I'd only go for a 25cm sellier Kelly if it's specifically meant to fill an "evening bag" desire. For a day time sellier, 28cm is my recommendation. The proportions, shape of a sellier looks best in 28cm.
 
You don't seem to be feeling a 25 - trust your instincts on this one.

As for DH: assure him that the 25 is gorgeous, and would make a perfect secondary Kelly (HINT HINT!). But if this is "it" (at least, for now/in his mind), you need something that will be really versatile and move from day to night.