I have the DTS and the RTS, and the DTS is by far my favourite of the two. I do a lot of paint work and the DTS is the go-to sander of all my 6 sanders. The RTS comes in usefull sometimes, but I use it only when the DTS doesn't fit. The DTS' bigger pad makes it much more comfortable to work with, it has better stability, and the tip also makes it a lot more versatile.
Dust collection with these sanders is excellent, even if you don't use a vac, because they sort have their own vac built in. The suction it delivers is very effective.
If you decide to get a Festool sander, you'll find them very different from what you're used to with that DeWalt of yours. There's no comparison. Of course you can expect that with a sander that's 5 or 6 times as expensive. The DeWalt feels to me like hollow plastic with the motor of a cheap RC racer while the DTS/RTS is a solid piece of steel with the motor of a very expensive record player. You can hear the difference by the sound, which the video by andvari nicely demonstrates. The Festools also handle a lot better and have less noise and less vibrations, which your fingers will appreciate after prolonged use.