Tom, I've used both the Ameristep Brickhouse and the Double Bull T5. There are some things that make a difference, and they are related to the stealth mode of things when hunting turkeys from a blind.
1. The material - nylon on the Ameri blind is very shiny, even on a cloudy day. Most times the turkeys make it out very easily, even when it is partially concealed amongst the trees. The DB canvas seems to be invisible to them, even out in the open.
2. The windows - the Ameri blind's are too big for my liking, and if they don't have the shoot-thru screen on them, turkeys notice it. To open/close the shooting ports, they must be zippered. With the nylon construction, it's rather noisy. The DB uses flaps on the shooting ports that connect with a hook onto an elastic loop at the top of the port, no zipping. Open and close at your disgression very quickly and silently.
3. The doorway - The zipper on the Ameri blind is very noisy, to the point where I don't even want to open/close it when located nearby roosting areas. I would rather leave one side of the blind unstaked and tip the blind up and crawl in. The DB zipper system on canvas is very quiet.
4. Visibilty - I've tried the Ameri blind out in the open.... no way, it doesn't fool them. Place the DB out in the open.... and they don't even flinch.
5. Rain - the Ameri blind sounds like a million little drummer boys beating down on the stretched-out nylon. The DB doesn't sound much different than rain hitting the foliage nearby. There is a huge difference in this.
6. Roominess - they both are about the same, and I think a 64" longbow can be used if canted. Gotta get familiar with the interior structure and know how to be situated and how to cant the bow in relation to the window you're shooting out of. I use a 58" recurve held vertically and no problems whatsoever.
7. Emphasis - the Ameri blind needs to have the shoot-thru screen attached to have complete confidence in concealment, even with the black interior. The nylon isn't as "black" as the DB's canvas because when daylight enters the blind, it has a sheen to it. The DB T5 does not have shoot-thru screen on the shooting ports, because it doesn't need it... seriously.
I've been in and out of both of these blinds in the last 5 days, and nearly every time I'm in the Ameri blind, the turkeys act suspicious. Never with the Double Bull. Just today I watched turkeys walk by the Ameri blind from my location in the DB... they acted spooked. I have complete confidence with the DB in full sunshine, but the Ameri blind must be in the shade to even feel part way confident.