That's like asking who is hotter? Ginger, or Mary Ann (on Gilligan's Island). It depends on who you are asking.
I don't think one company's knives are better than the other; just very different for different consumer tastes.
For the past two years, I've been on the Spyderco bandwagon. It's strange because I never cared for their knives before then. However, I'm totally sold on Spydercos and my next several purchases will only be Spyderco. Why?
1. First and foremost, they make very unique and distinctive looking blades. There is no mistaking a Spyderco with any other knives. They have a cult following like Porsche owners, or Breitling watches. Not everyone likes them but the ones that do are gah-gah over them.
2. All their inhouse knives are built so well. All companies have their lemons but the quality control and management at Spyderco are superb and on par with ISO standards in my opinion.
3. Sal Glesser. Here's a guy who takes his personal time to talk to the community he serves to find out what they like and don't like. Not a lot of Spyderco's competitors do that.
Now Benchmade is pretty innovative too, and I really like their knives; although I questioned their quality control a couple of years back. I credit them with starting the race (or should I say rage) for the better and stronger lock. When they started mass marketing the Axis locks (apparently it's not a new idea) other cutlery companies were coming up with variations (SOG, Cold Steel, et al.). In addition, the 710 Axis is...well, there's no point in saying how good it is as most of us realize that it kicks the butt of folders costing much more.
FTC
BTW, I vote for Mary Ann!