Also Collari's car had some (loads of) parts from other brands.
It is not wise to determ your choice on the base of what wins the WC. I know the slogan "what wins on sunday sels on monday" but if I have to follow this I have to get a Kyosho M3 with Serpent steerblocks, Serpent clutch, Serpent tank and a Mugen gearbox. And ofcourse a Collari engine.
Then it is up to you if you can make it to a winner and that is a difficult task. Some brands were using harder plastic you can not get, the engines running in the final are far away from the consumer version and you will never know all other secrets. And beside that, most of us do not have the driving skils of Collari....
Mugen is wise to buy. It is worldwide supported and the car is strong, that is making my choice driving Mugen.