I've got 500's and a Maverick.
The only real difference between the two is that the Maverick uses a fore-end that has the action bars pinned directly to the fore-end. The M500 uses a steel tube that has the action bars welded to that, and the fore-end just slips on. If you want to change the fore-end on a Maverick, it won't be easy, unless you convert it to the M500 action bar tube arrangement.
Also, the Maverick has a cross-bolt safety on the trigger group. I actually prefer this arrangement to the tang safety on the M500.
Otherwise, they are the same gun. The stocks and barrels and more parts interchange.
The only cheap thing about the Maverick 88 is the stocks and fore-ends are black plastic. Not that this is a problem for a home defense shotgun.
It's 90% of an M500 for 75% of the cost. You can't go wrong.