I tried Patxi's for the first time last week and IMO, their pizza rivals Zachary's.
There were two differences I noted: 1) The crust at Patxi's is more of a traditional cornmeal crust and not the flaky, buttery crust from Zachary's. 2) Patxi's sauce is smoother and more garlic flavored than the chunky sauce at Zachary's.
The pizzas were made with fresh, high quality ingredients which perhaps justify the high price ($16 for a small pizza which is more than enough for 2 but probably not quite enough for 3). I also really liked the selection of draft beers.
I respect that the menu has only pizza and salads - they're keeping their focus. However, given the upscale (relative to) pizza parlor decor, I'm surprised they chose such a limited menu.
All in all, for someone living on the peninsula, I have no reason to make the drive to Rockridge anymore.