Just my opinion but some Deep Dish Bullitt out back while you keep your stockers with the same color would look sooo nice... Plus you only have to buy 2 new rims versus 4...
I dunno, should you do it? Have you no opinion of your own?
If you want what everyone else wants then by all means go for the FR-500s or the deep dish rear Bullitt rims. Then you'll have just one more Mustang with FR-500 rims or Bullitt rims. If that is what you want, then go for it. You'll fit right in with every other Mustang.
Not a fan of FR500s either. I love 04GreyGtUSAF's recommendation of the DD bullitts - especially if you want to stay 17s and save weight and cost of the tires themselves.