I've never owned an Emerson, and I've only owned one CS, a Recon 1 clip point combo edge.
However...
I've often looked at both brands. First impressions are important, which is why I've hesitated buying one. Here are my impressions based on many factors.
Emerson:
Major fit and finish issues in the past, though supposedly things have changed.
Steel: 154CM is a good all around steel, nothing great. Truth be told I feel for what EKI charges, this steel is outdated.
Liner lock--My least favorite locking mechanism as a whole, though some do it better than others (Brous and Spyderco GB come to mind). The only Emerson I've handled I felt the lock bar to be rather weak, a major concern for me. It is easy lock to disengage than most though.
Wave feature--a novelty to me. I owned a Kershaw Emerson briefly, I never really felt the need to wave it, and when I tried remove it from my pocket with out waving, it halfway opened, stuck in my pocket, then snapped closed on my finger. Trip to the ER and a couple stiches later, that made the wave a no-no. Thanks, but no thanks. I owned a waved Spyderco Endura, which was vastly easier to take out of the pocket without it opening, but it still wasn't for me.
Made in the US--Take it for what it is. You're paying more money for what is not necessarily a superior product.
Frankly, I will never own one.
Cold Steel:
Tri-Ad lock is vastly superior to the liner lock IMHO. But it's also a bitch to close one-handed unless you have large hands and strong fingers (like me).
Very grippy G10 on many of their models, easily shredding pockets. But I can tell, you ain't gonna loose one falling from the clipped position.
Ambidextrous, good for the lefties and those who swing both ways.
Steel: AUS-8A--Immensely strong knife, average at best steel. Kinda like a 6 cylinder Chevelle. You can get by, but do you really want to?
Steel: CTS-XHP--My experience with this steel is in my Spyderco Manix 2 sprint, and it is far and away my favorite stainless. If CS can produce it as well as Spyderco, then they will be on par with and even ahead of their competitors.
Made in Taiwan--A detractor for many, but once you've experienced a Taiwanese Spyderco, your impression will change. While CS is not on par with the level of the Taichung Spydies, they are still very well made with good fit and finish.
Variety--Many models to choose from, they aren't all super tacticool beasts.
As a whole, tactical knives do not interest me. At 6'4" and 245lbs, I'm usually left alone. Good friends of mine are in a band from the south side (Chicago) and I've been to most of the bad areas and some very seedy bars, and never have I felt threatened. If confronted, I'd rather plant a fist in the BG's face then run for it than fumble for the knife in my pocket, which the aggressor will likely see I'm going for something and attack before I can respond.
I am really excited for the new and updated Cold Steel knives. I've shied away due to the AUS-8, but now they are calling my name.