1) Actually light travels about .55c in fiber and electricity travels about .6c in copper.
2) Unless you have a dedicated fiber to your house from your ISP, you're still sharing at the node. Residential fiber fiber uses "passive" fiber. This means you receive all the same data that your neighbors receive. So when your neighbor is watching Netflix, your fiber modem will also be receiving their packets, but filters them out.
The upload on passive fiber is also shared via TDMA. While one person on the local node is uploading data, no one else may upload. This is broken into small time slices so you still get reliable pings. But it's like a bunch of people who want to talk and only one microphone, you just keep passing it around the circle and let each person talk a little at a time.
So really, that 1gb of bandwidth is shared at the node.
3) DOCSIS3.0 for cable, supports sCDMA, which allows multiple people to talk at the same time. This means you don't get time slices and also increases bandwidth to the node. A single 6mhz physical channel supports 127 virtual CDMA channels for an aggregate of ~5gb/s of bandwidth. There can be multiple channels, so, 8 physical channels will supports about 40gb/sec of bandwidth. From the node to the ISP is all fiber.
In theory, DOCSIS is actually quite nice and in practice it is only "decent" and some times a "nightmare". What it all comes down to is how your ISP setup the network. It is possible to have a really crappy all fiber network, and it's possible to have a really good DOCSIS network.
Most companies that are willing to install fiber to the home are also willing to go the extra mile and make sure the network is properly balanced.
In practice, cable networks suck because they're ran by really greedy corps that are use to having a monopoly and refuse to upgrade their networks unless they absolutely have to. You also run into the "phantom" connection problem with cable as electrical signal problems can be very hard to track down.
Also, you don't have to worry about signal strength for the most part with fiber.
In practice, go with fiber.