On my last trip to Seattle I rode BoltBus up and Amtrak back.

I found BoltBus to actually have a more comfortable (less bumpy/vibrating) ride quality. However in the bus the seat forced me to slide forward, and there was less legroom.

My biggest complaint about Amtrak is that they extensively sell scenery as the reason to take the train, and so many seats are located next to the pillar - on my second to last trip, I had absolutely NO view from my seat, unless I turned my head 70 degrees. Let's just say after three minutes of that, it gets VERY uncomfortable. Fortunately, I was able to move to one of the ADA coaches with my son to get a better seat.

The other issue is that Business Class is a joke. You get slightly more legroom (not that you need it), and a lousy $3 coupon. The last time I was in Business Class, I made sure to arrive super early. The fine Amtrak personnel claimed there were no single seats left and gave me an aisle seat with someone else. Ended up spending my entire trip in the Bistro car. Yet, other people who clearly arrived after me got better seating arrangements. On my return trip (in coach) I had an entire aisle to myself, for less money. The biggest problem with the Cascades isn't so much the ride quality, but the God-awful seat assignment process.