+++1 for the AA-54.
I borrowed frequently a MFJ-259b from a friend, and I never really liked it much. Frequency was always all over the place, and you could never dial it to an exact frequency. Also, if an antenna showed a 1:1 on the analyzer, it was always higher on the rig. Batteries never lasted very long either. Could've been a bum analyzer, but, wasn't overly impressed with it. I tried the frequency counter a time or two, and just never felt like it worked, or was accurate.
I saved the money and pulled the trigger on the AA-54, and it's in a whole other league than the MFJ. You set the frequency, and it stays. You set your antenna, and if the AA-54 shows 1:1, your rig is going to show 1:1. I have yet to learn just what all it can do. Plus, the ability to hook it to a computer and print out results is pretty nifty too. There are also several bits of software made for the AA-54 that will do some impressive things.
IMO, you won't go wrong with the Rig Expert over the MFJ. I also concur that the AA-54 is worth the few extra bucks over the AA-30, but, I'd use the AA-30 with just as much confidence.