I'd say neither of those. The calf on the Skye isn't particularly suited for rain (it looks bloody awful when wet!), and I mentioned above that C&J themselves don't consider shell to be a good leather for poor weather footwear.
Out of all of C&J boots, the Snowdon is the only one that stands out as a poor weather boot.
The Islay and Arran would also do, at a push, although the dark brown Islay model's studded Dainite sole isn't the best when it comes to traction. From my own experience, the Ridgeway is the best rubber sole out of C&J's options in poor weather as the irregular tread pattern (compared to commando or studded Dainite) gives better grip than most in wet conditions.