I guess it depends on what you want to do with it. I could play a few downs of football in ABS armor and just abuse it (then again, it was my sandtrooper so the gouges were fine). The TE2 I certainly wouldn't do any stunts with it or abuse it, but would stand up well to normal trooping.
I'm not sure I'd call the helmets fragile though. Fragile to me is a resin C6 clone helmet (ask me how I know). The tusks and bottom opening are prone to cracking but can be repaired with a little TLC. Again, I've had and seen a few crack there, but my garrison mate has his loaded up with fans, RomFX, etc. and does some serious trooping in his.
As Mike said it's always a trade-off. Some people are just more comfortable in ABS knowing it will take more abuse. On the other hand, trimming HIPS is easier and it can easily be reinforced from the inside.