Nothings beats good timely rains. Nothing beats a good nutritional supplement along with timely rains.
The differences in feeds will be in the mineral, trace mineral and vitamin package which are the most expensive additives to feeds. All those are very key. Also, the combinations of proteins in the feed are important as an antler when growing/finished is 44% protein, 22% calcium and 11% phosphorus. Those combinations of protein sources are used at different stages of digestions in the deer's stomach system. These minor details not on a feed label are the difference in feed brands. The key to a good nutritional program is that you see those improvements every year no matter what the weather is doing.