Got it! I am a happy (mostly) PG500 owner. I love the versatility of being able to direct grill steaks or burgers on a weeknight and smoke a brisket on the weekend all using the same rig. So it was nice to free up some space on the patio by getting rid of my gas and charcoal grills. Also nice to not have to have to get propane tanks filled.
I don't know how the cook chamber volumes compare, but the amount of things you can fit on the indirect side of the PG500 is a bit of a limitation. However, I mostly just cook for me and the missus so it is OK.
One other drawback depending on your environment is the lack of insulation on the PG500. On windy days here in the midwest or when cooking in the winter it is pretty inefficient. I would guess the FEC is much better insulated? I don't have any familiarity with the FEC, but that would be a consideration. I would also consider the PG1000 over the PG500 due to this. It would be interesting to pit the 2 side by side and compare pellet consumption.
Hope this helps...