Aks are very accurate and have a reliable v3 mechbox.
Mp5s are a little less accurate due to shorter barrels and have a good-but-less-reliable-than-the-v3 V2box.
I still prefer mp5 due to size, look, size of mags, amount of accessories, etc.
Both are good guns. If you like bigger, get the ak.
Grand Poobah of T.W.A.T.