Think there are trade-offs when you change water temps. Cooler is probably going to cause a bit more condensation, but cooler air is more dense so you can fit more of it (and vapor mixed in) into your lungs. Some people find it refreshing, too. Keep in mind
@DieHard s post about exhaled vapor being wasted vapor!
If I go with other than room temp water (actually kind of chilly this time of year), I prefer warmer water. Not super hot, but about as hot as it gets from my tap (115 - 120 F?). I find it more soothing. I don't re-heat it as it cools, but actually used one of those coffee warmer things when I was playing with this technique a couple years ago. Needless to say, I didn't really find it worth it. That warmer is tucked away in a drawer somewhere! Although I don't really notice a difference in effectiveness of the vapor, it does allow me to vape easier with a little bit of a sore throat or a cold. This is a pretty big deal for me. Know many want nothing to do with vaping while their sinuses or throat are suffering, but seems to make me crave the relief of a good sesh even more.
Same as pretty much everything... give all a try and do what you enjoy most. You may even find sometimes you like cool water, sometimes warm, sometimes room temp - or sometimes none!