Not sure if you've done this yet but you can give Chris (Circle D) and Andre (Edge) an email through their respective websites to see which converter they suggest.
I'm going to say they Chris will suggest his $900 custom billet converter which has a 2800-3000 stall like you're looking for. I read somewhere that the $400 circle d is just a stock converter with a couple new parts. I don't remember where I saw that though.
The edge converter you're looking at is similar to the $900 circle d in that it is a custom billet converter and a 2800-3000 stall. I think if you're going to compare them look at those 2.
That being said I think I'll be going with the edge converter just because its price is not $900
You probably can't go wrong with either since both companies have happy customers.