I think, from your statements that you are really drwan to the scene in the Mission especailly along 18th Street and Valencia. That isn't Noe Valley but the closest Pac Heights can come to anything similar is Hayes St.
While Noe Valley and Pac Heights can be similar the proximity to really new and attractive shopping and resturants leans towards Noe.
BTW the Mission has BART to take you downtown or bike along basically flat terrain.
Here are some other thoughts:
Noe / Dolores
1. weather wise, Noe / Dolores is typically warmer
2. its the "foodies" epicenter of the city
3. no real views unless your really high up on the hills
4. Dolores area is more bike friendly
1. its safer...not that Dolores isn't safe.
2. better for outdoorsy types due to easy access to the beach, Ft.Mason, Crissy Fields and even the Presidio.
let me know if you've got questions or need anything else!