I just happen to have a Hydrogen and an Alpinlite with overfill. The Alpinlite is heavier but it is warmer and more comfortable. I'm not a big guy but I do tend to thrash about a lot in my sleep. So I don't want my mummy bag to make me feel like.....a mummy.

I never feel like I'm struggling to heat up excess volume in the Alpinlite. On the contrary, that bag gives me more room to wear extra clothing without compressing the loft and allows me to fine tune my insulation.

I'm not convinced that a WM bag is any warmer than any other bag of similar cut and loft. But they tend to be lighter. Of course that edge comes at a price. I think WM has a good grasp of what the their target customers want.