Hi
The RTS is actually my next sander to get. I've been considering the DTS but since I already got the RO90 with the delta pad I will opt for the RTS. The way I think is:
Good for 90 degree corners and straight edges.
4 corners to wear out on the paper insted of 1 (or 3).
Not as wide as other sanders.
In the future I might go for the LS130, same paper.
[2cents]
Festoolviking