In the modern era of MMA, there have been two systems for scoring fights, the Ippon system used in Japan and made famous by PRIDE, and the ten point must system used in the US. There are several differences between the two.
In the ten point must system each round of the fight is scored, the winner getting ten points and his opponent nine or less based on the criteria. A round can be scored a 10-10 round, or a draw, but MMA judges in America seem to almost never score rounds this way. In the ippon system the fight is scored as a whole, that is the rounds are not tallied and their is no points system, but rather a decision either way, or a draw. The word "ippon" means one full point, in the ippon system the winner is awarded that one full point, and their is no halves or heirarchy as seen in Judo's ippon system. There is just one point awarded, and the recipient of that point is the winner. This is of course except in the case of a draw, which is now almost as rare in Japan as in the ten point must system in the US.
The next difference is the criteria used to determine the winner. In the ippon system the effort to finish the fight is the first and most important factor in a decision followed susequently by damage, combinations & ground control, takedowns & takedown defense, and agressiveness. In the US it is effective striking, followed by effective grappling and then last effective arena control.
Where things start to get hazy is when one considers what is the true definition of, say, effective grappling. One can not simply break it down into,"He's on top so he's winning",or ,"He's in guard so he's winning." If one considers Fedor Emilianenko, Gary Goodridge (when he was still good), or Tito Ortiz, they have all been great at HURTING people while trapped in the guard. If one conversly considers Mark Kerr he has shown an inabilty to do damage from the guard, and was often prone to being broken down in this position and actually controlled himself, even if not submitted. On the other side consider Minotauro and Royler Gracie, they are extremely dangerous from the guard bottom. Conversly look at Gilbert Yvel, he is often able to opponents in his guard but has no attack from there. So is taking someone down and staying in their guard good? Sometimes, sometimes not. When you have a rigidly defined system of scoring, as seen in the ten point must, it is broken down into verbage like "takedowns into the mount" or "passing to the mount", but this is frequently not representative of what is actually taking place. If someone like Fedor can control and do damage in the guard, why would he need to pass to mount where he is more easily reversed? It seem to me that a decision should be rendered based on the fruits of the position, not the posistion itself. This is similar to the ippon system, which scores points based on the attempts to end the fight and damage, rather than who is in a certain position.
Another intresting point is that is worth noting is that the ippon system works infinantly better in Japan also because of the round length. For the ten point must to work at all, it requires equal round length, and Japanese fights are often a longer opening period, followed by one or more shorter periods.
Another flaw that seems inherint in the ten points must system is the fact that judges almost never score a round anything other than 10-9. I have seen less than a dozen rounds actually scored 10-10, 10-8, or 10-7. This is a necessity for the system to actually reflect the happenings of a fight. If a fighter comes out and squeakes out the first two rounds of a three round fight and then is decimated in the third, who has actaully won that fight? In the current thinking of US judges it would be unanamously 29-28 in favor of the first fighter, no matter how badly beaten he was in the third round. This happens far less in the ippon system, and Hendo Ninja at PRIDE 17 is a good example of this. For the ten point must to work properly judges must be willing to score rounds something other than 10-9 when the situation calls for it.
The issue of judge bias is equally distributed in my opinion in both systems, if an American judge wants to give a fighter a decision no matter what, he can do it just as easily. It is harder to defend than an ippon decision, as the judge has to defend why he scored each round the way he did, but either way a judge can render a dishonest decision if he wants to.
Both systems have a different way of scoring things, place different emphasis on certain things, and favor certain styles of fighting. I perfer the Ippon system, but I don't mind te ten point must if it is executed properly. Either way, the current system isn't accurate in reflecting the events happening inside the cage here in the US. We must either adress and fix the problems with the ten point must, or get knowledgeabled judges scoring on an ippon system, regardless, the US needs a change in judging or it could seriously hinder the growth of a wonderful sport.