I have just sold my Quad 12L's and bought 22L floorstanders. The 12L's were brilliant, so I went all out. Only difference as you'd expect is a more extended bass, however, I also feel that there's more of a tighter and perhaps clearer/better defined soundstage on the 12L's - punchier and more distinct in a way. The 12L try's harder, the 22L is laid back.
Maybe I'll get another pair, but still settling in with the 22L's after only a few days - will run them in a bit more for sure, and also try bi-amping (to Quad 405-2's).
Key advice - buy the best possible stands you can find for the 12L's (Sound Organisation Z5750 or equivalent)