Gotta love Somerville. So many places within a stone's throw from each other on Winter Hill; I needed to sort them out for myself, so we tried all of these places (again) within a span of two weeks or so, for comparison sake. At each place, we got at least a half a standard cheese pizza, so we could better compare one to the next. Here's my take. Agree? Disagree?
MAMA LISA'S has very tasty NY-style pizza. Pretty similar pie to Caesar's outside of Union Sq (Somerville, not Manhattan). Probably my favorite on the Hill. Good flavor, crust, cheese/sauce ratio that tends to make a nice slightly soupy mix when hot. One of the great bonuses of this place is they'll sell you a half a pizza, as long as it's cheese (so they can use the other half for slices). They deliver, day and night, and are open 7 days.
Like Mama Lisa's, PRIMO'S serves a nice NY-style pie. They may have the best crust on the Hill, for both crispiness and taste, and make a very good pizza. Good cheese, sauce, ratios.
LEONE'S is classic. Also delicious, but totally different from the others. Very cheesy, very saucy. Bit of sweetness to both the sauce and the crust. All pies (whether you get a "tray" or a round) are cooked in pans and so are a bit thicker than your standard NY-style. No delivery.
WINTER HILL BAKERY sells all kinds of Portuguese breads; sweet and not. But they also usually have a tray of pizza you can buy slices from. It's more the old-school "tomato pie" kind of slice you find sitting out on the counter in Italian specialty shops and delis. It's meant to be eaten at room temperature, and I'm a huge fan of this sort of tomato pie. Theirs is not the best ever, but it is well put together and delicious.
I'm not a huge PINI'S fan. They deliver and are always open (even holidays, usually), so we order from them sometimes, but they're by no means our go-to place. Crust my least favorite of the 5 I've listed -- definitely ask for your pie crispy or well-done. We've had better luck with their specialty pies (veggie is good) than their standard cheese.