I bought a van system from ionics, but I did look at pure2o systems too, as they are cheaper, and here is my thoughts on them.
From what I could see they use basically the same metal tank cage and brackets that ionics systems have, and the tanks are more or less the same too. But, the filters are different.
For example, my ionics system uses linear filters that mount sideways and change colour when theyre worn out, but pure2o systems use those blue resin bottles that you refil. Secondly, i dont think you get a water softener with a pure2o system, which supposedly makes the ro last longer, but i dont know. I dont think its essential anyway, its just nice to have, so probably doesnt make much difference.
Thirdly, the reason i didnt get pure2o in the end was because they dont do a hot water version, and thats what i wanted. But other than those things, i think the pure2o systems looked pretty good. Solidly built etc, i doubt you'd have much bother with one. The fact that its backed up by ionics is a good thing IMO, and they are cheaper too. If i hadnt wanted hot water, i 99% probably would have got one.