from what I can see these are the key differences I have visibly seen as reported by comcast itself and its users.
1 - comcast has a fixed usage limit, although now its more flexible
http://www.techspot.com/news/48643-c...-soft-cap.html
2 - users have reported triple US bonding with some channels also utilising QAM64 instead of QAM16.
Also curious of the customer density per node on comcast vs VM.