I'm trying to decide where to celebrate my birthday/once-a-year dairy binge. I'm a big believer in the subjectivity of any "best such-and-such" exercise, which is why I'm going to give you a little information before you cast your vote on which is the better pizza.
First, my pizza preferences. I'm a Bostonian. The standard by which I measure all pies is the pie from Stella's in beautiful Watertown MA. The cheese, while great, is not the star - it is in a role supportive of the thin, char-edged crust and the slightly piquant sauce. The whole thing glistens with just enough oil to give the faint taste of olives and enhance, rather than impede, the crunch of the crust.
Next, know that this pizza would be consumed with a group of about 6 people. I'm no fool for decor, but room to accommodate me and my friends comfortably while I enjoy my pie is essential.
Incidently, I enjoy a glass of vino with my pie. A liquor license or a BYOB policy is helpful (tho not essential).
Finally, you should know that I'm leaning towards Grimaldi's so that I can follow up the pizza with ice cream from the Factory (it is after all a dairy binge). But I'm ready to be persuaded that DiFara's is so superior it is worth giving up fresh ice cream for. I'm also ready to have some other treat for dessert, if there is great stuff in the neighborhood.
PS - Searched on both - many of the links are broken. Just so you know I'm not a lazybones.