I'm on my second X-45 and like it quite a bit. It's also the most "bang for the buck". You should check with Saitek on what constitutes a "refurbished" unit. My guess is that the entire electronic guts are replaced which would include the switches and pots.
The reason I'm on my second X-45 is that I wore out my POV hat switch and couldn't see an easy (for me) way to replace the switches in it (although I've heard that it can be done). The first stick lasted about 3 years of which only maybe one year could be considered "intense" use. Other than the POV hat I've had no trouble with either stick. If the entire guts are replaced then there is no reason it wouldn't last as long but, for the price, a brand new one is a pretty good deal ($70- $80?).
I personally don't like the ergonomics of the X-52. The controls are poorly positioned and aren't nearly as easy to use as the 45. I have absolutely no problems with the rudder rocker on the throttle and see no reason to invest in actual rudder pedals (and I use rudder alot). I've also tried a twist grip and didn't like it. Lots of times I found myself trying to track a target while not realizing I was inadvertently twisting the grip. Airplanes can get real squirrly real fast when you don't realize you're flying uncoordinated and I never got used to the twist grip. I did make some modifications to the rudder gains for the X-45 and have the sliders near the bottom for the first 1/2 and then ramping up to full gain at the end. This gives some very precise control for tracking shots while still giving me full authority for snap rolls, guns defense, etc.
Mace