I put it on the GTI when it was pretty much brand new, in May. the windows had never seen any sort of treatment. Cleaned the windows then prepped them with the alcohol pads, then applied the product. It's still noticeably effective to date, 8 months and 8k miles later. There was no noticeable hazing like you get if you miss buffing out a spot of Rainx. On my other cars using rainx at about 30-35 rain would be driven off the windshield. Aquapel doesn't do that until about 50. So Rain-x seems better in city driving from what I've seen.
I don't get any of the wiper chatter that rain-x is notorious for, so that's a definite plus. For me, rain-x gets applied way more often, usually every other car wash.
Just my experiences with both. YMMV