most of us use a 5 or 6 stage rodi filter. The 6 stage does have one more filter, but honestly filters and resin refills are pretty cheap. What you gain back is pristine water with zero nutrients or other junk in the water which is by far the best way of insuring what exactly goes into the water.
I run a 5 stage currently but only cause I couldn't afford a 6 stage when I bought it, if I had been able to I would have bought a 6 stage for sure, and may do so in the future. The 6th stage actually may last a bit long then a 5 stage filter too so in the end you prolly spend about the same on filters.