you might want to break this down further into easiest to program, afford, monitor, etc.
if you're interested in just the OCFA and/or city fire departments, then any analog Motorola trunking scanner will do. Due to the nature of the system, a non-trunking scanner will make it frustrating to monitor, at best. As for ease, its really a matter of perspective. the 785 has been blasted many times as being hard to program: I had no problem.
Now, if you're interested in monitoring the whole system that fire is on, that's really a whole other animal.