We have the Ford E-450 chassis with the V10. Love it. Would I say Ford has a better chassis/engine? All depends....and your factors may vary.
Bottom line for me is this: Both the GM 6.0L chassis and Ford V10 chassis are good. Ford has made/sold them 100/1 over the Chevy (my guess at the ratio). To me, Ford has done a better job of selling the chassis for commercial/OEM use such as box trucks and RV's.
It seems the GM/Chevy chassis are used on shorter RV's.
Bottom line for me, I do like the Ford chassis and with their investment in the new 7.3L gas engine for the new Ford chassis, it tells me they continue to improve upon it.
Sorry not a specific answer as you may have wanted.