I prefer a dedicated 22lr trainer. I like my main rifle ready to go and dont want to have to deal with switching out the bolt/mags and cleaning more
I dont think the SW 15-22 makes the best trainer. I bought a Tippmann arms m4-22 elite. It is compatible with most ar15 parts and has the same grip, stock, trigger and handguard as my main AR15. I also like the fact that my son can use this to train with me as he is younger and the 22 is better for fundamental training stuff due to less recoil and sound
Yes it was more expensive, but it is a fun gun to shoot on its own as well. Never have issues with it and it is more accurate than my 10/22s
Other option would be a build, but the Tippmann was the easy button