Roundhouse carrier is also called Honda style carrier. They have the enclosed carrier housing that an aluminum carrier with eccentric axle hole slides in. The eccentric hole is how you adjust the chain.
The difference is the chain adjustment. That's it. Roundhouse allow you to properly and effortlessly adjust the chain tension and keep it. Yamaha never put it on factory for the banshee. Yamaha's design is terrible and often fails on high hp quads. Don't waste your money on another stock carrier. Buy a new swimgarm with Roundhouse style carrier mount.