Lets break down your question a bit. Delta, or triangle shaped sanding pads work into corners easier than a plain, larger square or rectangular pad. Next, how large a surface area does your sander need to work, like do you sand large areas on a cabinet often, and just need corners sanded every now and then. OR, you need corners taken care of primarily, with the "field" or main surface areas handled by some other sander you own?
For corners, the Deltex sander 93E is small, works well. Larger delta sander would be the DTS 400 EQ, and if you want totally tricked out 3- mode sander, say one that just MIGHT retire some of your other sanders since it handles field AND tight spaces, the new ROTEX 90 DX model. With the RO 90 you simply swap round pads out for the Delta shaped pad in seconds with the mode button turned to the Delta mode, and you're off and running into your corners. Figure out how large you want to go, all 3 sanders are of much different weight and handling configuration. Decide which works best for you. I own both the Deltex 93 and the new RO 90. I may still get rid of the Deltex since the RO 90 has more power and a larger surface sanding area. We'll see.......................
Now back to just rec/square pad sanders. I also own the RTS 400. Nice 1/4 sheet sander, good dust collection, and not as "buzzy" as many other 1/4 sheet sanders. While I doubt you're looking for a 1/2 sheet sander, I highly love my RS 2 E. Even though it's a 1/2 sheet sander, and much larger than 1/4 sheet models, I can still work it into corners and use it one handed. Truthfully though, if you need a detail sander, you should GET a detail sander since it's what you really need, or seem to need from your post. And yeah, I own a BUNCH of Festool sanders [embarassed] [embarassed]