The DA-21E is a Orbital polisher with a 21mm throw area for max coverage and is supposedly equivalent to the the Rupes polisher which all professionals seem to use..., price seems to be good. Why would you buy something more expensive ?
Gtechniq C2v3 for body work, spray on wipe off and people claiming they have had it last 6 months. I don't know of a spray on wipe off for wheels though.
DAS6 is the go to dual action polisher, I was very happy with mine and only got rid of it when I bought a rotary.
Haven't used it but their other DA polishers are very good as they are claiming it is an improvement so should be good.