Quality wise it shouldn't even be compared. XM 99.9 percent of the time has better paint apps. It's part of what you pay for. SS Brown Wolvie is a great interpretation and a solid add to any collection.
Better paint? No. Better QC and production? Probably, yes.
But any day of the week, I'd take a Sideshow prototype vs. an XM prototype. There is really no contest as to who are the better artists.