I owned both at one time. The Mossberg works, looks cool and is cheaper. That said, I only have the VTR now. I think it's a much nicer gun.
The VTR feels like a real gun. The parts are made of metal and all the accessories like stocks and forends bolt onto it. It has a heavy target barrel, 30-round magazines are cheap (~$20), upgrades are available to lighten the trigger. I think it's easily as nice as the SR-22.
The Mossberg is all plastic -but there's really nothing wrong with that. There will be visible seams, takedown involves lots and lots of screws, extra mags seem to be hard to come by, and there aren't any upgrades available. However, it does have a railed forend and a carry handle, so bolting on cool accessories is an option. just keep in mind that EVERYTHING is plastic, including the rail for the optic. Since the hand guard on the VTR doesn't have rails, its another $80 expense to add a floating forend if that sort of thing tickles your fancy. Also I assume you are pricing out the VTR with the fixed A2 stock, whereas the Mossberg is adjustable.
Ultimately the difference is price and what you're going to do with it. WSS sells the Mossberg for $229. The VTR is around $400. Adding in the rails, stock, a scope etc. there's a significant price gap between the two which is reflected in the product you get. If you just want to plink and send a few hundred rounds downrange, either will be suitable. If you think you want to play around with AR parts and squeeze extra accuracy out of your humble 22, then the VTR is a better rig.
Basically my conclusion is the Mossberg is a much better value if you're happy with it in stock form. I prefer the weight and feel of the VTR and I'm sure anyone who likes to tinker will be much happier with it down the road.