Greg,
Lots of options out there, and ultimately, you're the only one who can answer this one correctly. But I'd take in all the various factors of a particular cartridge before jumping on it based on velocity/performance alone. Things like how easy is the cartridge to form (if you need to make them), or how readily available are factory cases (a significant consideration in the XC itself)? What about dies? I haven't checked on these recently, but when I first set up for the XC, David's dies were the only ones available and he wanted a mint for them. Cases were an issue as well. He's had several lots of cases run for this, some not too bad, but at least one was real crap. Very soft and gave all sorts of problems when they hit the street. David developed the XC, as Mike points out, as a competition cartridge. Nothing wrong with that, but it means that some emphasis of the design is going to be focused on factors that may not be important to a hunter or a varminter, and in some instances, may even compromise what you're after. And that's exactly why we have so many options out there today. Just take your time, and look at all the various tradeoffs and advantages of each, and you'll come to the right conclusion for you.