Campy is way better than Sh*mano in my experience. Needs much less adjustment, seems to last longer, better quality. It is also better designed (well in my opinion - I mean the Ergo levers are way better and more comfortable than the STI ones - and they don't have cables erupting everywhere either! It's also way more classy. OK in some cases it's more expensive (but it is Swings & Roundabouts - I've seen some Campy stuff like Cables and hoses being cheaper than the Sh*mano stuff) but I think for the added benefit I've found from it definitely make the extra cost well worth paying. I run Centaur (cross/Winter bike) & Record (Road Racing Bike)
Have got Ultegra on my time trial bike though, it does run ok, but if I had it built up from spec instead of getting it off the shelf on offer I think I would prefer to be running Campy on it.
XT stuff is good on the mtn bike, but then I've never ran SRAM Mechs or Shifters. I would say that the SRAM chains are a lot better than the Sh*tmano ones too - they seem to split and rejoin better, and with the powerlink it makes removing them for cleaning a lot easier.
Generally I would say I use the stuff with the Campy on a lot more, so it's not even a case of one taking more of a hammering than the other. The time trial bike gets used only for that, and obviously a few runs, but has needed way more adjustment than the road bike which is used several times most weeks (indeed virtually every day in the summer)
As for those mudguards, well last night when my lights died I had to take a detour along an old overgrown and muddy railway line (sections closed to the public too so not as if the drains had much maintainance either). Yet despite this the wheels are encrusted in much, but the frame and the rest of it was pretty much clean!! Definite plus in my book as it means I just have to wipe the few mud spots off, and wash the wheels - rather than the whole bike all the time which I had to do with the previous winter one!