It's a pretty subjective thing. I started out packing a Warren and Sweat stand that was like wearing a biplane on your arse in and out of the woods. By comparison, the Viper is a fanny pack.

However, I'd call the viper moderately bulky, but not uncomfortable for hikes under a mile. If you're planning on hiking for more than a mile wearing your stand, the viper is going to start to get uncomfortable.

I can't vouch for the bullet backpacker, but a friend of a friend of mine has one and I don't think it seemed much more comfy to pack than the viper. A little perhaps, but I still wouldn't want it on my back all day.