I think most of those are pretty much the same thing, probably just branded stuff. Maybe strc has an extra step of quality control, since they are selling like triple the price.
A clue I had, the aluminum upgrades for Axial EXO, at first I found the unbranded version selling really cheap in chinese ebay, asked where can I get those stuff in US, and got told to go strc (much more expensive though), a few weeks ago I found a integy branded version being sold on ebay, priced similar to the chinese stuff price.
You get the idea then.