I agree with I_27 that proportion is a critical factor in beauty. There was an excellent documentary presented by John Cleese "The Human Face" which went into the importance of proportion very well.

That said, for me big or small, tall or short is in itself unimportant but it does affect the body parts that get more attention and the activities I like to do with that particular gal - if a gal's got a big meaty ass then spanking is on the menu - if it's hard and bony then I will simply refocus elsewhere. I guess my ideal would be one of each size then I get to have a variety!