Al Pompiere or Sora Margherita?
they are quite different - Sora Margherita is a crowded bustling skinny room with paper tablecloths kids can scrawl on - Al Pompiere is in an old palazzo, as I recall, you go upstairs to a large airy room - when we went there, this was several years ago in the winter - it was rather empty for lunch - their regular menu is not cheap but I think they have a touristic deal - two or three courses, from the menu, for a fixed price.
We liked both, but Id give the nod to Sora M - the guy at the door should level with you about how long your wait will be and you can make your decision.
be sure to order oxtails (coda di vaccinara) or gnocchi if you are there on the canonic roman day of the week for those dishes.
I love them both: you should go to lunch at Sora M and then DINNER at Al Pompiere. The zucchini flowers and the carbonara...I'm salivating now.
The simple things at Sora M that I had last spring when I was there were just wonderful: a meatball in tomato sauce, sounds everyday, but it was magic.