Upper Crust tends to get mixed reactions from a broad range of people in Boston. Some love it, some say it's overpriced, some say it's the best--others: the worst. I'll try to give you as objective of a review as possible--because I usually do that, I think.
Let's start with some circumstantial logic. Upper Crust is a decent chain with a lot of location in the Boston area and they win numerous local awards every year. They specialize in Neapolitan style pizza, which denotes very thin triangle slices with a mild presence of sauce. It's good, neither heavy in your stomach nor greasy--no excess oil surplus here. However, consider that some will say that it gets very hard and chewy if not eaten while fresh--I have experienced this before.
I'll assert that on Newbury St. Upper Crust's antithesis is Bostone. Bostone is not a chain so it lacks the availability that Upper Crust has. Also an award-winning pizza joint, Bostone offers Neapolitan style pizza, but shifts focus to Sicilian pizza, which denotes thick, square-shaped pizza with a heartier consistency than Neapolitan. Bostone has notably greasier Neapolitan slices than upper Crust, but their Sicilian pizza is excellent in all variables.
Both are similarly priced with a slice coming to around $3-4. Although expect a large price jump from the Neapolitans to the Sicilian, which can cost anywhere between $18-40 depending on how many toppings and if you get a small or large. If you do get a large Sicilian though, you will see why it's so expensive--they are colossal.
Get both. See if you prefer Upper Crust's Neapolitan or Bostone's Sicilian. That'd be the easiest way. I prefer Bostone's Sicilian, more filling, more irregular (Neapolitan seems more the standard) and the texture is amazing--a blend of crisp crust that crunches when you bite and soft and doughy on top.
Bostone: 225 Newbury St., Boston, MA 02115, 617 536 9451, www.bostonepizza.com
Upper Crust: Boston, Cambridge, Brookline, Watertown, www.theuppercrustpizzeria.com