NVRAM is great as long as you don't have to install the socket on the board first, there are dozens of us who pulled traces on the boards and had to send them out for repair because of this luxury mod, why do I call it a luxury mod? Because you can install a remote battery pack in 1 minute and be done with it. No need to chance damaging your CPU over it. If you have a Sega, or Stern Whitestar CPU, by all means, install NVRAM, because all you have to do is pop out the old chip and install new chip. But with WPC you need to be desolder old chip and install a chip socket, and that's where the devil in the details will get you.
PS: I have installed NVRAM on (if memory serves) 9 of my games. I have a Hakko desoldering gun and I've gotten pretty deft at this kind of stuff now, but I still recommend a remote battery holder for the majority of collectors in my circle.