Not sure about preferred location, I put mine in the laundry room on the wall about two feet higher then where i tapped into the cold water pipe that feeds the washing machine but thats cause it worked there lol.
I also got it, because it supposed to be more efficient and use less water. I can't say for sure because the it was my first RODI, but in theory it makes sense.
easy to install and it does seem to work, I've noticed less waste since I did the upgrade but have not gotten out a stop watch and bucket.
I don't think the height matters much, a few feet on a 1/4" line is not going to make much difference on the pressure.