I've owned both a Mossberg 590 and a Remington 870 (and others), and there's no question in my mind that the Remington is the better quality piece. But, the Mossberg will certainly go bang every time you pull the trigger. It's not junk. If it where me I would buy a Remington every time versus a Mossberg.
As a matter of fact, there's an 870 on sale at Davidson's, item # 5077, for only $310.00.