I actually prefer Robeks over Jamba Juice, for a couple of reasons:
1) Their smoothies are less icy and more thicker and richer
2) Their smoothies have more flavor instead of mostly tasting heavily like fruit or yogurt - they're more balanced
3) They have a lot more food options (don't know about you, but I like a tasty snack with my drink) and their vegan cookies are incredible!
However, the only negative is that there are a limited amount of locations in Arizona (I used to live in California, and there were TONS of locations there), so if you're ever near one in AZ take the opportunity and load up!
I loved this location especially because of the friendly staff and fast service!