Well, when it comes to spending money, either coating will ensure your wallet is substantially lighter.
I can't speak to Imron (though I know many will claim it's better than AwlGrip), but I had our E35II AwlGripped in 2005. The paint looks virtually as good today as it did when it came out of the paintbooth. In my opinion, it was $6000 well spent.
That said, you'll find reports by others who claim their AwlGrip is beginning to fail after about 12 years. I think this has a lot to do with location, use, UV exposure or lack of it, and the coating's maintanence itself. I think it's important to have the hull 'AwlBuffed' (for lack of a better term) every few years. I think that goes a long way towards the paint's longevity. Conversely, using harsh cleaning/polishing agents will most likely contribute to an earlier demise.
Long story short: Our boat's appearance was greatly enhanced with the AwlGrip. But - (and this should be obvious) - unlike a well done hand applied enamel or epoxy coating - Awlgrip and Imron require professional application and equipment. Exceptions aside,these are highly specialized processes.
YMMV
Capt Dan G>E35II "Kunu"