First is the bowl size, which I think should be in the 14-20 ounce range. Any smaller and your glasses will always be full. This might sound appealing, but in reality makes the glass a poor choice for capturing aromas. Larger than 20 ounces just seems excessive, and bulky for that matter, making the glasses more difficult to store, wash and use. Suburbanites' opinions may differ.
Another dimension you should take into consideration is the height of the glass. This is tied in with the volume of the bowl to a certain extent, but is also a design factor with many glasses. Long stems can be weak, making storing your glasses a pain in the glass. Oh, and did I mention my dishwasher's glass rack is 7 and 1/2 inches high?