I am a huge fan of the quality of my spectrapure ro/di. The filters last a long time, materials used feel strong and durable. I have recently had my hands on a BRS model and was greatly impressed.
A lot of what you need depends on your area water supply. You can find the report usually in your local government website. Then you can check out the BRS YouTube Videos that talk about selecting the right one for you!
I watched the BRS Video ( I have really been becoming a fan of BRS videos in the past few days. It figures it would be a BRS video which would help me out here.)
I think I have decided to go with the BRS 4-stage Value Plus system.
Their videos on RODI units are superb. Great information and very accurate. My Dad is a Control Room Operator in a Cogeneration Facility, he works with RO units used to run power plants. He says that they put a years worth of training in a 5 minute snap shot in some of them.