The answer, if you can stretch to it, is to keep both pairs. One of the rules for jeans is that one length will not work on all occasions. The longer ones will be great with high heels, or when you want to slouch around a bit. The other pair will be more practical, and will look right with ballet pumps, flip flops, pretty sandals and flats in general.

If you can't go for broke, pick the length that most suits your lifestyle and your taste in shoes.