Much smaller than a full-sized .45. I'd recommend starting with something halfway between them, a Compact. So if you're carrying a P220 or P227 now (or something similar sized), try moving to a P229, Glock 19, HK P2000 sized gun first.
The reason I say this is you are used to that nice long sight radius which has so many advantages for practical shooting. Jumping down to a P224 gives up a lot of that, and to what end? If you aren't having trouble concealing a full-size .45, I say stay as large as you can.
This coming from someone who carried P224-sized guns for years and just moved up to a Compact, and I'll never go back.
All that said though, the P224 is a nice little package. Shouldn't be less accurate than a P229, but YOU may be less accurate with it due to the reasons above. You also likely won't get a full grip on it, which may or may not be an issue. Should be much more concealable due to the short grip.