I use army surplus. Basically, the trousers (pants to the USians) are loose, fasten at the bottom to stop getting caught in the chain, and are ripstop, so when I take a tumble they survive and stop me from losing skin. Plus, they are very, very cheap.
An accident bad enough to destroy a pair of camos, isn't going to leave you with legs to put in them, so I'm covered either way.
Then again, I use my bike primarily for commuting, here in London, where the biggest issue is avoiding being mashed by things with engines. Survivability, rather than comfort, is the buzzword.