Yeah, you're pretty much spot on: Nothing is more fun to shoot than a suppressed .22 pistol, and a suppressed AR-15 is MUCH more pleasant to shoot than unsuppressed, especially indoors.
Here's what I have: I don't have a .22 can yet, but I have an SWR Octane 9 HD and an AAC 7.62 SDN-6. The SDN-6 lets me shoot any rifle caliber from .30-06 on down (it works great on 5.56 and 300 Blackout) and the Octane lets me shoot any pistol cartridge from .357 Mag on down.
And the Octane is one of the few pistol cans that works great with .22 rimfire; all other pistol cans I know of are either sealed or they'd be a real pain to take apart if leaded up. But the Octane is the same design as their Spectre 2 suppressor, just bigger and with a Nielson device. You'd think the Octane would be louder than the Spectre with .22, but it's actually noticeable quieter. I guess the extra volume makes up for the larger bore diameter.
The Octane is a lot lighter than a .223 suppressor, but it's still noticeably bigger and heavier on a .22 pistol than a real .22 can. That said, on a steel Ruger MkIII the Octane isn't too big or heavy and it's crazy quiet.
If you wanted to REALLY cover as many calibers as you can, you could get the Octane 45 HD instead of the 9; it's the same diameter and only about an inch longer. I might have gotten the 45 instead of the 9 for maximum versatility but it wasn't out yet when I bought my Octane 9.