No doubt the Onans are noisier than the portables. Being able to set the portable away from the TC also helps. But we still like the convenience of a one touch button to start the on board unit up, and no setting up and taking down. There are also a few things that you can do to help with the noise. I installed rubber bushings on all 4 mounting points. I also installed B Quiet sound shield to the inside of the genny compartment and the Onan resinator on the tail pipe. I can run my Onan and comfortably watch TV in the cabover and can hardly hear it. Down below in the main area of the TC it can be heard but its not annoying to us. I think alot depends on the construction of the TC itself. AFs are built very solid and the more solid a TC the less vibration thru out the unit you will get. I use my Onan from time to time and its always worked well and never let me down.