There is no SR for Space. SR vs. FP for RSR is a toss up, it depends on the time of day or other factors that you can't predict. For me, SR vs. FP sometimes depends on if I want to go back later to use the FP. For Splash, that's a no. For Indy, you do skip a lot of the queue by doing SR. It's also highly dependent on how many
DAS returns and HA returns are waiting to go into the safety film. It will depend on if the possibility of saving a lot or a little bit of time (you won't know until you're down there waiting) is worth missing some of the themed queue. Otherwise, I don't spend a lot of time worrying about FP vs. standby. If I want to ride Star Tours and the line is barely out the door I'll just get in it instead of pulling an FP and coming back later. If I want to ride Screamin I'll usually just do standby because FP or SR save such little time when the line is short that isn't not worth it.