I used to be based at FUL 2 years ago, currently based at SNA.
FUL, all the way.
FUL
is a GA airport, period. They cater Cessnas, Beeches and Pipers. SNA is my current base and I can only comment on resident services there, as I've never had to use either FBO. The controllers at both airports are very good.
Agree with Jeff that coming in over El Monte (EMT) and ducking under the Class Bravo was always my preferred route coming down from the bay area (LVK). If you are coming in via Camarillo, go over the Burbank Class C (4800') and dive towards the Rose Bowl to line up for El Monte and getting under the 4000' LAX Class B shelf into Fullerton.
Just make sure you have flight following (assuming VFR) on the way down or pick it up near Santa Barbara or Camarillo as the airspace gets busier. They guys and gals at "SoCal" are very helpful keeping you out of trouble.
Fullerton can be difficult to pick out of the ground clutter if it's hazy. GPS is your friend in the LA basin. Don't be afraid to tell the FUL tower that it's your first time and you're having trouble seeing the field; they'll help get you pointed in the right direction.
Current gas prices: FUL= $6.20 SNA= $7.50.
I have had good experiences with both AFI and General Aviation at FUL. Both seem pretty good to me. AFI has truck service and "pump serve" gas, meaning you pull up to their pump and they will gas up the plane to your spec. for you. I never had any trouble letting them fuel my plane while I was there.
Come on down and enjoy your stay at FUL.