When the other companies say they do trans tuning, they are most likely just bumping up the line pressure and that's it. Try 3-4 different tunes from the custom tuners out there and no 2 tuners have the same shift strategy... And you can request specific tuning options for your tranny like early TC lockup, or lockup in 4th gear, or stay locked in coast, or firmer shifting, or different shift points, etc... Edge, Hypermax, Banks, none of them do that. You can't call or email them and request them to change something about your tune that you want changed. That's why its called generic, it's one size fits all.
And unless you have an SCT with SCT's canned tunes, it's not the SCT that is superior, it's the tuners who write the custom tunes. It's just simply the best platform for the tune writers to write their tunes on.
Buy an Edge tuner, do you need to give them your PCM strategy? Or your TCM strategy? Do they ask if you have headstuds? Do they ask what mods you have done to your truck? Nope. The custom tuners do because they know that each of those questions will change how the tune is written for your truck. The tune writing for my truck will be different than the tune writing for your truck, different PCM strategies, different programming, etc.
Now you can get decent power gains from en Edge, but if you're looking to squeeze the most HP out of your truck, then the custom tunes will win 10 times out of 10. That's why the most Edge advertises is 120 RWHP gain, if you get the unlocked platinum model, its 100 hp for the regular juice with attitude. Get an SCT 3015 from Innovative with his tuning (just using them as an example) and he advertises gains of 180 RWHP. So with an Edge, the most you're going to get is ~360-380 RWHP. The Innovative will be somewhere around ~440 RWHP on his full fuel tune. And most custom writers are all pretty close on RWHP numbers. It's the nuances in their tuning that make them stand apart from each other.
As far as SCT canned tunes tranny tuning, couldn't say if its better or not, never used them. However Edge has gotten the reputation for being tranny killers... Both in 7.3's and 6.0's.