I initially used SafeChoice and liked it very much as a regular feed, but my boy is a super easy keeper, so I switched to a ration balancer.
The store I normally buy from does not carry Nutrena so I tried the R.B.s that they had. Like them very much, but decided to switch over to the Empower Balance and I love the stuff.
I go a little out of my way to get it, but one bag lasts a long time.
Like the other RBs I only give a cup (bakers measuring cup) per feeding along with his flaxseed and hoof supp.