I recently read this information from Quality Whitetails magazine.
Deer prefer the white oak acorns over the red oak due to the lower tannin content. Tannin is a chemical produced in plants to deter predators from eating them. You can taste the difference in the two. The red oak acorn is much more bitter. The tannin also causes trouble for an animals ability to digest protein. Deer's saliva contains compounds that bind to the tannin and reduces the protein digestive problem. The red oak family acorns contain 2 & 4 times the amount of fat content compared to the white oak.
Also the red oak group produce larger acorn crops when compared to the white oak.