CPR's are usually preferred to get away from a u-tube overflow. If a Lifereef is a standard U-tube than I would assume that the CPR is better. I visited the Lifereef site and it says that it is better than other U-tube overflows and it says that it is better than CPR type overflows that don't use U-tubes.
Too bad I've never had to oppurtunity to use one. I've used almost every other HOB overflow box made.
CPR's syphon tube is part of the construction of the overflow box and cannot be removed. From reading Lifereef's site, it appears that Lifereef would be better because in the event of a poweroutage it will restart. CPR overflows will do the same BUT if the Aqua Lifter Pump should fail or if the AC20 Powerhead should fail than you'll be without a way to keep or restart the syphon.
I'd give Lifereef a try but look up reviews on it to be sure. The less accessories that can fail, the better.
I've had Aqua Lifters go bad but luckily nothing happened. Plus, there are cheap rebuild kits that cost (usually) under $10 for Aqua Lifter Pumps. I've never had an AC20 powerhead fail on me tho but it can always happen.
With Lifereef there is nothing mechanical to fail. So long as it can keep it's U-tube from allowing air to get in, then it seems to be the best way to go.