For the home, FIOS is far superior to Cablevision. For business, FIOS internet blows away Cablevision, latency and jitter and quality of service is far better than Cablevision. FIOS service totally sucks. Cablevision service for business is then best I have ever seen in 30 years of being in this industry, their response time is hours for a problem, FIOS is days.
From a technical aspect:
FIOS delivery method (fiber vs analog/coax) makes for better internet, faster speeds and as mentioned little to know jitter or latency. Also, with FIOS, you are not sharing bandwidth with your neighborhood, you get what you sign up for, unlike Cablevision. For the residential TV user, when changing channels there is no delay when the next channel populates with FIOS.
As mentioned, Cablevision has awesome hotspots, Verizon has none
Cablevision has no taxes and therefore is less than the best deal you can get from FIOS
Cablevision service is far better than FIOS, but with that said, FIOS very rarely needs to be serviced.
I have both at my house, FIOS for the business and Cablevision as a backup, a few years ago I was pro Cablevision, not anymore, as a heavy IP user for phones and other things, FIOS internet is much mor stable than Cablevision.