I wear zip offs because I can't find cheap versions of the same pants without the zippers. I did manage to score some Mountain Hardwear pants that are similar.

I also have 5.11's, but only wear them when I must - when I'm on search and rescue, or when heavier, durable pants are called for. Tho mine are nylon they just aren't the same. I like lightweight pants that dry in no time.

Long pants keep the poison oak, ticks (if you treat with permethrin), scratching branches, sunlight, and dirt off your legs.