As others have said, it's all about trying different shorts on to see what fits you, and then personal preference (do you like leg grippers, a minimal chamois, a wider waist band, a certain length of inseam, etc.).

I personally like my Pearl Izumi Symphony shorts ($100); they have a good length inseam for me (8 1/2"), the waist band is wider which I like, and they have grippers. Now on the other hand, I did not like my previous Giordana shorts due to the horrible, narrow little waistband and becasue the lyrca was just a little too thin in my opinion (at least on the shorts I got a year back and they were "mid-range" shorts).

You can read about PI's different shorts on their website.