If you can glue an FX, you can spray paint an ATA suit of polystyrene in gloss white with some ease. If you can fit in both, I recommend ATA... every image I have seen of it looks sweet.
Heatshock is right... "It is your choice" and it is good to have choices. As soon as I can fit into ATA... I am selling my FX. And as far ar the durability of HIPS verses ballistic-grade ABS... and since I have worn HIPS clone armor and ABS clone armor, it is in how you care for it. Frankly, I have been pretty tough on the HIPS components of my clone suit... but, it repairs well. If you plan on trooping 4 times a month, you may wear it out faster... just take care of it, and you will be fine.
Crawling around on gravel, as a former clone armor liked to show photos of himself doing shows the strength and durability... but is it kinda dumb too, since, in the end... these are just really nice costumes. And not battle-wear. But if you foresee yourself fighting in it, go with FX. HAHAHA!!!
Seriously, get the ATA!
John