I personally just liked the idea of being able to use the factory tensioner system, and not having to permanently modify the head. The weak point in the factory tensioner is the rubber rollers that just do not like running marathons in their old age. I figured if i can just improve upon the rubber roller issue, I'll have a very solid and reliable system. I understand the advantages of the slipper, and it definitely has its place. The advantage of using the rollers is if you're on a budget, which a lot of garage builders are, you have the ability to only purchase one roller if that is all you need. The rubber upper roller tends to get trashed quicker than the lower. It is definitely advantageous to replace both rollers while you're in there, but If you're in a pinch and can only financially justify replacing whichever one is chewed up, you now have that option instead of replacing the entire system. I'm also just a fan of working with what you've got. If you've got a roller tensioner assembly, you can just upgrade the rollers and not have to deal with grinding away the cam chain passage to fit the slipper if you do not want to go that route.