Here let me throw a 5th tire in the mix to make things even MORE complicated
, Maxxis Bighorn 2.0. A riding buddy of mine ran them on his 2012 Sporty 400, he was very satisfied with them. They work great in all conditions. Now to the tires you listed Reapers are a great tire but to heavy for a 400 in my opinion. Will the machine handle them??? Absolutely!!! But just to heavy IMO. Now which BC's are you considering the HTR's or the K299's. If its the HTR's then you have considered another fine tire. Little lighter then the GR and therefore I would consider it a good fit for your wheeler and riding conditions. You can cross the BC K299 off your list if thise were the BC's you're considering. Only ITP ML's I would consider would be the XTR. Decent tire in all conditions and it's of a lighter construction being a 6-ply. I have no knowledge nor experience withe the QB line of tires.
So of these three "we" have mentioned (GBC Grim Reepers, Kenda Bearclaw HTR, and ITP Mudlite XTR) for you application they're dead even, couldn't go wrong with any of them!!!!
BUT the Maxxis Bighorn 2.0 is head and heels a better choice!!! The 2.0 can go toe to toe with the heavy weights like the Grims and Bears but it can also fly with the light weights due to the 2.0's lighter carcass!!!!!