All things else being equal, size and strength will win.
Because of that, steroids can augment one's ability to fight insofar as the added strength/endurance can contribute to the brute tools required to inflict damage.
Darksideninja--
Hate to tell you bro, but UFC is not real streetfighting by a LONG shot. The primary difference is that you will never ever see a truly qualified adversary coming. Street fights are not fair, and they are not stopped. UFC may be the closest thing, you could be right about that, but still, nowhere near the genuine fight for survival. UFC is a SPORT. An interesting sport, to be sure, and a somewhat brutal sport.
I notice on this board a bizarre preoccupation with toughness in general. I think that there could be a correlation between those who fear smallness and those who fear weakness. The reason that many cringe at the thought of being small is because they dread the possibility of other people thinking that they are weak. Look at Ninja's comments. For him, the ultimate nightmare is to be considered weak. He asserts his ability to fight natural. Here's a newsflash, ninja. You cannot fight, period. You are too easily controlled mentally. You want to become a better fighter in one day? Learn right here on this board that you are afraid of being considered 'not tough', and conquer that particular fear. Once you understand that it is not important if others think you are tough, you will be much tougher than you are now. Right now you waste a lot of energy trying to CONVINCE yourself and others about something very insignificant. The physical tools of fighting are something that anyone can learn. The mental clarity required for survival outside of the ring is another thing entirely.
This continued speculation about who could beat up who is purile. The fact is that you will never EVER see the toughest individuals inside any sportfighting ring. Why? They HATE fighting. They realize that to pointlessly risk one's health for an AUDIENCE is an exercise in self-ratification. You think any of the UFC fighters are there for any reason other than to prove how tough they are? The desire to prove that, in and of itself, renders them one notch below a genuine survivalist fighter, simply because they routinely expose their mental and physical resources. In the real world there is no 'squaring off'. Remember that.
I certainly respect the dedication required to become an excellent UFC fighter. I know a few of the successful ones. They are respectable people in all regards, at least in my experience. There are a couple of them on these boards. The best of them will tell you right now that they are aware that the survivalist elements of streetfighting are removed from sport fighting.
Here's the difference for those of you who still don't see it:
In the ring, it's about fighting only. On the street, its about NOT fighting. A ring mentality in the street will get you killed.