It depends, but mainly I'd recommend going with a dedicated build.
For an AR, I went with a dedicated rifle. It uses a CMMG 1:16 twist barrel with their bolt, which is the same as the conversion kit but uses a different collar for the dedicated .22LR barrel. Twist rate and not filthing up my center-fire rifles were the incentive for going with the dedicated build rather than just throwing a conversion kit in an existing rifle. I'm glad I did what I did, because it gets FILTHY. It has proven to be extremely reliable and accurate, though.
I've not had success with "trainer" type .22 handguns that are meant to be a copy of a center-fire gun, or the conversion kits. They just aren't reliable. I have a Ruger MkII and MkIV that are incredibly reliable and accurate. While they don't mirror the manual of arms or the ergonomics of my center-fire guns, they are still useful for practicing the fundamentals, and far less aggravating than the other .22 handguns I've owned.
For an AR, I went with a dedicated rifle. It uses a CMMG 1:16 twist barrel with their bolt, which is the same as the conversion kit but uses a different collar for the dedicated .22LR barrel. Twist rate and not filthing up my center-fire rifles were the incentive for going with the dedicated build rather than just throwing a conversion kit in an existing rifle. I'm glad I did what I did, because it gets FILTHY. It has proven to be extremely reliable and accurate, though.
I've not had success with "trainer" type .22 handguns that are meant to be a copy of a center-fire gun, or the conversion kits. They just aren't reliable. I have a Ruger MkII and MkIV that are incredibly reliable and accurate. While they don't mirror the manual of arms or the ergonomics of my center-fire guns, they are still useful for practicing the fundamentals, and far less aggravating than the other .22 handguns I've owned.