In reply to Sam Ash:
No experience in summer alpine, but I have both, and the alpine light are an odd beast. They are very stretchy, much more so than the mountaineering pants, and they're much less wind resistant, and a closer cut. I've worn the mountaineering trousers skiing, a lot, with various layers underneath, ranging from thinsuate liners in Dec/Jan, to merino leggings in early april. I still haven't worn the alpine lights much, preferring the Forclaz 900 (now renamed 500) Warm, which are more wind resistant.
Then there's the Simond rock pants, if you can cope with bright orange. I haven't been brave enough to try them yet... But at £35, I ought to give them a go...
http://www.decathlon.co.uk/orange-rock-pants-id_8305030.html
There are plenty of comments on the mountaineering trousers over the years on UKC; have a search.