We went with PSI because they were SO much cheaper, and we went with reverse osmosis because if we want chemicals or nutrients added to our drinking water, particularly for the children, we'd rather do it manually

.
I was a little concerned about the higher water wastage, but ours goes into our grey water stream and the taste is SO much better.
We also use their shower filters because dh was particularly concerned about chlorine gases - and I realised last night that the only two children in our house with a croupy cough are the only two using chlorinated hot water

. I noticed the chlorine smell when I was bathing the baby, and kept meaning to get a filter for the bath tap but just put it off - but I'll be getting onto it now!