I've always been partial to Sedona Springs or Aquafina...because they have the sports bottle tops.

just kidding...
There are so many producers of ro units now that there is somewhat of an industry standard, and brand names are only associated with sales deals or upkeep/maintenance programs...
It really doesn't matter too much which brand, just get one that you can get replacement filters from locally...being able to shop near you is key !
Greg