I train to be the best I can be. If you can handle a well trained opponent, then you can handle a untrained one. My point however is that they have a much more consistant level of skill because of the training methods they use. If a guy comes up to me wanting to train and he says he is a TKD blackbelt, I dont have any idea what to expect. He could be a pushover, or he could be a awesome kickboxer and cut though me. If a guy comes in who claims to be a BJJ purple belt. I know that he has major skills and I know the level of skill to expect from him.
This is a side effect of sparing. It boosts the level of skill of everyone involved. Lets say I have a great setup for an armbar from the guard. I learned it at a semminar and I use it with awesome success back at class. People are going to ask me how to do it. Hopefully I'm a good guy and I like my club so I show them. Other people are going to learn just by having me do it on them in sparing. Others are going to ask the coach how to defend or counter it. Within a months time that armbar isn't very great anymore. I need to learn new techniques if I want to get submissions. This cycle continues. I'm forced to learn better defenses, counters, submissions, counters to the counters, etc because if I dont I wont be able to defend myself from my partners.
At the same time, the higher skilled guys can use this teaching method to point out my flaws. When I first started I would get triangle choked left and right. One of the blue belts in the class would just triangle me over and over, I was never submitted by him except from triangle. Finally I learned how to defend against this and how not to put myself at risk of a triangle. With a sigh of releif he said "Finally, I was getting really bored of that submission", then he started working other submissions when we rolled. He noticed a flaw in my game and exploited it to the point of being rediculious so that I would learn how to defend it.
We had a guy in our club who lost a few fights to rear chokes. For two weeks when we sparred with this guy we would start with the backmount so he had to start from a bad position and defend the rear choke. He was submitted over and over (despite having been show, and drilled the choke defense) for about a week. Finally he learned how to make it work for him and I find him one of the hardest guys to choke from the backmount. I had to learn a few new ways to setup the choke just to have a chance. This boosts the skill of the whole club.
Eventually a new guy will come in. Until he does you feel like all this sparing has lead to no gains, you feel like all you do is get yourself bruised, beat up, tired, and weak. And then you roll with this new guy. And you realize that what was once fast, hard, and troublesome is now slow, telegraphed, and easy to defend. You realize that you can handle a bigger stronger less skilled guy easier then you could a month ago. And as you roll with this guy over the next few months you watch him become a greater challenge as he gains skill and understanding. And this pushes you to train even harder, so that you can learn new skills and strategys to keep him on his toes. You also get the understand that no matter how hard to train, how good you are, there is someone out there (and most likley someone in your club) that can take you.
I dont belive any martial art is better than any other. I belive some training methods are better than others. I belive any art can benifit from more sparing and more resistant drilling. I also dont think there is anything to lose by adding these to your training. I also dont spar to win. I spar to work on a my techniques. I was tapped out all night monday. I only tapped out a couple guys. The reason was that I was working on new material that was shown to me a couple days before at a semminar. That said, I do train to win. I love competition and when I go to one, I play to win. This does mean that I have to dedicate some sparing time to training with a competition mindset. But you do not have to have a competition mindset to spar.
I also feel this post over on bullshido lends itself to this converstation and is a great read (It is an explaination of the Inquiry Method of training) http://www.bullshido.net/forums/show....php?p=1016621