I have the AWR on my protege, been on for about 6 months or so and the paint (i'm guessing that's what it is, i don't think they are power-coated) right at the welds have peeled off already and is starting to rust a little bit...
so i'm not really a fan of that to say the least...that means i have to scuff and repaint that before winter to protect more...
I have no problem with a tubular design, i believe it to be stronger, but where there are welds involved, your item is only as strong as the quality of the welds and how well they are protected, that's where they break.
Whether it be a tubular, box, I, or X frame design, it won't matter (well, it will for stiffness, but trust me, mine are very stiff, especially with the urethane bushings) if the welds are not the best...
So for that reason, i would recommend a different company from which you order from than AWR, regarding their trailing arms that is.
My .02 cents, but it's what's I've experienced so far, i'm sure it'll take about 3-5 year for them to rust and break, IF... IF they do.