My experience has been that Space Mtn. runs out before Splash. So I would get that one first then watch that time like a hawk to get one before Splash runs out. It seems like most people head towards FL and Tomorrowland first thing, so Space is the one they get first. People generally don't want to get wet first thing, so they don't ride Splash (it doesn't build a line quite as early as Space) and they don't fp it as early either. In fact, if you get there at 11:00, get your fp for Space and then head over to Splash. It might not be that bad of a wait, esp if its cloudy and the crowds are a bit lower. If its broiling hot, it will be crowded too! But my experience has been that Splash fp's last longer, in fact for one of our summer visits, they didn't even have the fp machines at Splash open until the park had been open for an hour or two. They said they wanted to keep Splash from running out too soon. This was the norm for our June of 2006 trip, can't remember if it was like that last summer when we went or not.