I own a ar in .223 cal. and love it. There is so many different ways you can go as in modifying it. Ammo is cheap. At the gun show that comes to the Portland expo center there is a vendor that sells ammo for approximately 240 buck per thousand. There are company's that sell .22 lr conversions for the ar so you could practice shooting for cheaper. I don't have any experience with the ak.
Hope this helps.
Hope this helps.