What type of sanding are you doing - trims or floors?

Festool.

Pretty much depends on what you are sanding. My most-used hand sander for flat work is a Mirka Deros, I also like the newer Festool sanders with the smaller bodies (brushless motors?) I've got a half-dozen others for other purposes, from floor standing tools to tiny pneumatics -- drum sander, osciliating spingle sander, belt/disk combo, etc. Wish I had a wide belt instead of the drum.