Couple years ago Coldsteel was a bit of a joke unless you wanted an inexpensive (generally), and decent quality (generally) tool for killing a person. Then the Tri-ad lock came around and they've been reborn to a degree. Now they make extreme use folders with what is often considered the best lock in the world.
Benchmade has been making some of the best folders around for a long time. The Axis lock is very strong, smooth, and more user friendly than the Tri-ad. Benchmade uses far better steels and has a much wider range of designs. They also have a better warranty by a long shot.
If you are on a budget and need a knife to beat on and don't mind knives made outside of the US, Coldsteel may be a good choice if you find a design you like. They also offer monster folders, spears, and plenty of other odd items that other companies don't have competition for.
If you want a fine quality knife, made with high-end materials, US made with an incredible warranty, Benchmade is the way to go if you can afford to spend a bit more.
Buy CS, you can dig a hole in the wall, a tree, or whatever you like without spending much, and therefore not worrying too much about damage to your knife. With a Benchmade, you can take pride in your high quality knife and use it for years. Many Benchmades can take heavy use too by the way too, but not likely to the point of the current CS folders. But, the BM warranty offsets that.