My latest extension didn't have any engraving on the bottom. I haven't experienced any bent plates, but the sturdier material can't hurt as long as it's not going to interfere with insertion.
I'll pass on coyote extensions, I prefer my guns and mags black.
I'll buy Krylon if I think I need a new exciting color for 2014.
The TF extensions haven't made it down this direction that I've seen.
None of the BORTAC guys I shot the last 3-gun match with were using them (and they'd have been a big advantage in the match).