Both good bikes. The Giant is a touch longer, and has a couple degrees more slack fork angle. It will be better on fast, sweeping downhill trails. Trek will be a little more nimble in tight stuff and probably climb a touch better and feel a bit lighter in the front end.
I demoed the Reign and on fast downs, I loved it. I felt much faster than on any other bike I demoed. But I ended up with an Evil Insurgent, which I liked much better for the trails we have here, not many long hills. The Insurgent in the normal shock setting has similar geometry to the Remedy.