Let's say we have a 22lr 40 grain moving 1050 fps and a 60 grain moving 750 fps (can anyone do any better?). This gives us 98 ft-lbs and 75 ft-lbs.
Compare this to a 70 grain Speer RN at 1050 fps; about 171 ft-lbs. Almost 75% greater energy. Use a heavier bullet and you get even more power.
Another factor is that due to the much greater powder charge in the subsonic 223 (about 7 grains) compared to the 22lr (about 2 grains?) the subsonic 223 is going to be much noisier than any subsonic 22lr especially when suppressed.
Using a 300 whisper or 300 Blackout upper is much nicer. You get true semi-auto capability and much more power from the 240 grain bullet or supersonic 125 grain bullet. I never got any better than double the group size with subsonic 223 compared to standard ammo in my ar-15. If you want quiet, go with 22lr, if you want power and accuracy go with 300 Blackout.
I think buying specialty ammo is for suckers. Buying a single stage press will save you money in the long run, the short run if you are buying subsonic 223.
Loading your own means you do not have to put up with subsonic ammo that actually goes transonic/supersonic and is noisy, or ammo loaded so weak as to guarantee subsonic velocity but only runs 800-900 fps with a trajectory that rivals a mortar.