IME (2.5 sets of XCs, 2.5 sets Pro2s) for general UK XC riding the XC is slightly better because –
1) The bearings last a lot, LOT longer. XC bearings are simply fatter and beefier. Think looking side on at a Polo, rather than a Hula Hoop! 🙂
2) They have a steel freehub body and can be used with any cassette or SS cog
3) They are quieter. Pro 2 noise got to me in the end…..
The advantages of a Pro 2 are –
1) More versitile
2) Rear axle is possibly stronger (I've snapped 2 XC rear axles)
It took me 4 years to destroy (And I mean runied, really knackered) a Hope XC rear, and I destroy rear hubs for breakfast. That's the longest serving I've ever had, by a long way. And I never touched them for the first 2 and a bit years, and the front is still untouched.
I've only had 1 Pro2 (So far) last more than about 10 months without bearing or freehub problems…..