M12 vs M18 stubby?

Im seeking some clarification on the two stubby options. Theres so much content out there I’m getting a headache trying to learn this all lol. In my understanding the M18 stubby is on its 3rd gen, and the M12 stubby is on its 2nd gen, but the M12 has almost double the nut busting torque from the smaller battery as long as you get the 5ah?? Im seeing that M18s are selling for so much cheaper and at much better deals for battery packages and whatnot. Also the 3/8th’s anvils apparently have more torque than the 1/2??? Adds more to the confusion I feel like Im gonna end up buying every impact before I’m satisfied. If you had to buy one right now which one would it be and why?