AK, hands down.
What legs said. 7.62x39 AR hicap mags are a pain to find, and dont always work reliably.
AK mags are $6 and plentiful.
My SAR1 was $279, from AIMsurplus. Add $20 shipping, $10 transfer, 10 mags, and Kvar US made furniture..... and I got a bad*ss looking, lightweight AK for under $500.
Or, spring for a Global Trades model and get a nicer finish.