there is a HUGE difference between the FX55 and the 62, with the 55 being single core and the 62 being dual. Unless you're into OCing alot, I'd go with the X2 5200.
that's a nice observation there, but those aren't the two cpu's in question. he was asking about the 5200+ vs. the fx-62 (which are both dual core, btw).
the fx series have unlocked multipliers. if you want to overclock, then go with the fx-62. otherwise, the 200mhz advantage the fx-62 has is not worth the price. they both have the same cache size.
The FX line of AMD cpus is the gamer's choice and has unlocked multipliers for ocing. I trust you are looking into a new build and wanting general information on which AMD model to go with since you have a Socket 754 model board listed in your signature. The X2 models on the other hand are geared towards multitasking and similar to the Socket 940 models used for server cases soon to be replaced with quad core model cpus later this year.
The entire line of FX models for both 939 and AM2 boards is geared for performance with the idea of ocing in mind. This is why those come with the unlocked multiplier on them. The X2s like the Socket 940 server models are intended more for multitasking while a few models are still oc capable.