Water cooling is less stressful on the motherboard when moving the pc around since the bigger air cooled heatsinks can be heavy. Performance isn't enough of a reason for me since the the relatively cheap air cooled DarkRock3 is RM320(gbros) and its performance is close to the H100.

If you don't have any experience with WC and are more concerned with long term reliability and are not going to be fiddling around with your pc frequently, then stick with air cooling. Leaks do happen even with AIO. The lower end AIO WC like the Corsair H55/60 are only somewhere around the performance of an 212evo air cooled heatsink and more expensive(2x) and may leak so they are quite pointless so only the better more expensive WC make sense.