With the wealth of knowledge, experience and appreciation of the experience of music on this site, especially Unsound, of course Tom Thiel and many others, I am well on my way to an upgraded system with the relatively recent addition of 3.5s to my 2.2s. For serious listening beginning last month I can now alternate them on my new vintage B & K m200s with 400w/4 ohms, but still need to use my old integrated (80w/4 ohms) as a pre for now.
They are in different similarly sized rooms with different orientations, each opening to another room and likely a 2 or 4 AWG discrepancy in speaker cables and several feet of length per pair, so any comparisons between the 2 must only be taken as preliminary observations. The additional power really made the 2.2s shine in every way possible, not news to (almost) everyone on this site. My long held view that they were a very slight bit bass shy unless played loud was completely wrong, absolutely present for the mid bass with the 400w, somewhat more than the 3.5s even, but not quite as well defined. What was missing was the sub bass that one feels with the 3.5s. Outside of the higher frequencies, the 3.5s have a bit more of almost everything, especially soundstage and depth, and are easier to drive.
Love them both, they are more alike than not, and could never part with either because each gives a slightly different experience of the music, but I do listen to the 3.5s more. With their present configurations one could almost make the overgeneralization that the 3.5s lean a slight bit more to the analytical side while the 2.2s to the more impressionistic, but that would likely be modified and refined if all other things were equal.
As many others have said, each step up unfolds new insights and enjoyment. Funny how the more I learn the less I know, but I am enjoying the process tremendously.