@Buba Blend is right, you'll get a bunch of different answers from folks. I've never had a problem with city water, that being said I know there are some places that have terrible water that I wouldn't drink or grow with. So it really comes down to your situation. Are you using RO throughout the whole house because of existing water issues? If so then you should most definitely use the RO. If you have good tasting water coming out of your taps I would just use that and have it sit out for a day or if you need to use it right away you could use some ascorbic acid (Vitamin C) to neutralize the chlorine and chloramine if you're worried about it.