I'm firearms proficient but I'm out of practice and wasn't a great shot anyway... Should I pick up a 22 to polish my fundamentals? Or just practice with what I got?
HUH?!
You practice with what you want to shoot regularly.
If you want to shoot a .22 at home invaders determined to hogtie your entire family, jam socks in their mouths, wrap a yard of duct tape atop that, THEN steal all of your valuables ... then, yes -- absolutely, YES!: shoot at those thugs with a peagun 22.
Otherwise, you might meet them with a Beretta or H&K 9mm with a 15 round mag. If you're savvy, you might have a .45 in reserve, like a classic 1911.
Becoming proficient with effective firearms isn't cheap, or easy ... you'd best heed my advice then quickly search out a local gun club and find someone at least vaguely like-minded.