The 3020 is the "nicest" of the bunch, the 360 is the same thing, just the last generation model. The Altus is a little nicer than the Tourney, but not much.

Don't expect a huge change in performance though; the RD is only part of the equation: the shifters and chain/cassette also contribute.

I have a couple of 6- and 7-speed bikes and I find that a nice 8-speed chain with flared, shaped plates, like the KMC X.8 really improves the "shift quality" over the flat-sided chain that comes on a lot of 6- and 7-x bikes