Switch's sleep is probably a little better. I think waking up is slightly faster, and it discharges less battery while it's asleep.

The main feature I notice to be lacking on Deck in this regard is that you can't download updates while the device is "off." This doesn't really affect me personally because I can do background downloads with the kind of games I play without issue, but if I played AAA FPS type games I would probably find this quite annoying, since those games generally have large downloads and also require as much disk performance as you can muster.