VEPR's have thicker receivers, thicker barrels, and a wider and stronger front trunnion(to accommodate the thicker barrel) than standard AKM platforms...Basically VEPR's are more practical RPK's.
I like the 5.45x39 round... But I'd look into getting a AK-74 before a Vepr... Just my 2 cents. And get as many 5.45x39 mags as you can, they get hard to find, from time to time...