If by "best" you mean easiest and most convenient, then the
Disneyland website certainly is both of those. Buy your ticket, print it out, and head straight for the gates. Safe, reliable, easy.
If by "best" you mean cheapest, then the answer is no. There aren't discounts any more for buying your tickets ahead on the DL website. Some of the recommended travel agencies (e.g. aRes, GAT,
AAA, etc.) may have slight discounts on a 1 day hopper.