ANR pros: Good level of sound attenuation, you can still hear aural clues despite the noise cancelling, R-R solution.
ANR cons: Very Expensive for OEM approved system, hearing loss, maintenance intensive in the long term, not easily retro fitted.
Mini CEP: Very good levels of sound attenuation, easily retro fittable, affordable, not maintenance intensive.
Mini-CEP cons: Almost too good - aural clues can be lost, you stick them in your ears - some people don't get on with this, can stay in ears if fitted by the ham fisted.
Gentex now have
wire free cep available, which gets rid of the cables, this combined with something like the Pro Flight Gear 'zero G' comfort upgrade would be something that I'd happily recommend to Alpha helmet wearers.
If you're in the UK give these guys a call, Key Survival they distribute and service Alpha helmets on behalf of the OEM, and come highly recommended.