Fiber vs. 2 separate business-class cable
I like the idea of connection and provider diversity. Can you do cable and fiber? Or perhaps another medium like fixed-wireless broadband? Couple that with a multi-wan link balancer (like an Elfiq or Barracuda), and you'll have very good protection for physical location issues, as well as upstream ISP problems.
Speaking as someone who has multiple (3 now!) cable modems, I'd go fiber. The redundancy in the multi-cable modem configuration is illusory. All those lines terminate at one network and congestion or packet loss upstream can be fatal.