RO/DI. I have off the charts tds in my well, then 300 after the softener...that isn't terrible, but when you don't know what that 300 tds is, why risk it? Besides, it is cheaper in the longrun to have a ro system if you drink bottled water. I would never use my tap water for anything but dishes, laundry, and showering. But I mean, it is possible to have great tap water, just not better than an ro system.