We've used both. The Heifer Developer has less corn, more filler. Both are good rations. I would base the one I use on your heifers particular needs. The grower only has like 540#'s of corn per ton. I don't think that's too much for any heifer. If you are in an area that it's cold, I would probably add a little more corn myself. We are feeding 4 different heifers for show right now and they all 4 get different rations. I feed them based on what I think is the best for each calf to reach it's best potential. We have a base ration mixed at the mill, similar to the grower, then I change it and remix it here at home for each calf. Hope this helps.