Honestly, none. Why separate your party, unless that's what you really want to do. The rides that have single rider options aren't hard to get FP+ for pretty much any time, so it's not a "waste" of a FP+. I know for sure I've never done RnR in the single rider line and am pretty sure I've never used the standby line either. I know we've done standby for TT, but it's been many years...probably since before the current FP+ system came out.
We use Single rider on EE all the time. But that is because my kids will ride it 5 times in a row and I'm not spending that much time in a line just to ride next to someone I know. LOL We have also used it for Test Track but that is only when a regular FP wasn't open for when we wanted it. And we also did it for RnRC and I agree with the posters above that it is not worth it... I am pretty sure we waited longer to ride separate than we would have if we got in the regular line.
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