In reply to Roberttaylor:
Why don't you just get a cheap pair of cotton track suit bottoms instead. While I have never put on karate trousers before just by looking at some photos, I think track suit bottoms will be better. Karate trousers looks a bit too buggy, especially at the bottom - not that it'll make a huge difference.
If you are talking about indoors climbing, the most annoying thing I had found is not having a secure pocket as the lockers work with pound coins so I have to somehow carry the locker key with me the whole session without losing it. I got myself a cheap pair of trousers with military pockets that zip shut and never looked back.
Small thing but worth considering if you have those lockers where you climb.