This is one of those age old debates that has been hashed over here. I own both an E450 motorhome AND a 6.0 powered Chevy pickup and love them both, so I can offer a somewhat unbiased opinion on both, although they are different vintages and applications.
Noise and vibration- The V10 is certainly smoother and quieter at idle. The 6.0 has a certain V8 rumble and lope, not unpleasant but definitely there.
OHC vs pushrod- who really cares? I'm not going to tear either engine apart, so it doesn't matter to me whether it's pushrods or fairies with magic dust that open the valves.
GM makes a 4500 series cutaway with similar weight capacities as Ford, so that's not an issue. Supposedly the Chevy beats the Ford in a drag race and a hill climb, according to a video that is on the Chevy website. Something that video does not explain is why Ford has a significantly higher towing capacity. In fact, I can't find out anywhere what the GM GCWR is. My truck's is 16,000 and the motorhome is 20,500, although the motorhome has better gearing. Loaded to about the same weight, the Ford launches better on steep hills, getting going easily where the Chevy really grunts. However, my truck will pull a 6% grade loaded to 14K faster than the motorhome by about 5 mph.
My verdict? They are both good, drive both, and remember that you will likely spend much more time living in the coach part of the motorhome than you will driving it.