The ATI is aluminum. That's not very strong, and the tube will dent easily.
The Pro-Mag is also aluminum.
The Carlson's looks like a re-branded Choate, and Carlson has NO reputation, being new, so it's a crap shoot as too quality.
My advice is to just buy a Choate. It's one of the best there is and is a great price/quality value.
It comes in any length from 2 shot to 10 shot, in satin blue or parkerized, and comes complete with the extension, spring, a heavy duty follower, and the all-important barrel clamp with sling swivels.
Choate has been making extensions for a LOT of years, with the only older one being the Remington factory model. Choate has one of the best reputations for quality.
You can buy it from Brownell's or Midway, or buy direct from Choate for about $45.