open at the same time. Last year we stayed at Y&BC, and used it all of the time.
I'm sure someone out there has done some kind of feet/yard/mile analysis (Robo, maybe?), but you need to hustle, regardles of the entrance, if you want to hit the key attractions (Soarin, Test Track, and Mission Space if you are up to it). We always do Soarin 1st, becuase you can usually do it twice in a row before the crowds build up. Then we head over to Test Track, and either ride it, or get a FP, and ride it later. We can then do the rest of the attractions at a more leisurely pace.
This assumes you get there at park opening.