Don't forget that unlimited fast passes start tomorrow and now you won't have to make a choice!
You are exactly right. You should always book TSMM first, but RnR should still have FP times available. If you have to stand in line at lease TSMM is entertaining to look at.You're more likely to be able to get a Fastpass for RnC later in the day
Not entirely true.
You DO still have to pick one or the other as part of your first three; the tiers do still apply in that regard. After your first three, the tiers go away and you can pick any rides that still have FP+ times available.
From what I'm seeing, as was the gist of the thread I referenced earlier, TSMM is much less likely to have FP+ available after you use your first three than RnC. Therefore, if you're wanting to do both on FP+, it makes more sense to book TSMM in advance and then hope that there is a time available for RnC.
Register on WDWMAGIC. This sidebar will go away, and you'll see fewer ads.