I found that my connection is now rock solid after moving from ADSL. My brother is watching twitch 24/7 or iPlayer, Playing games and downloading. And I can just fire up a game and play happily with no lag.
Likewise with me. I can be downloading to our lines full capacity (or thereabouts) whilst my brother can still be on his Xbox with zero lag and my parents are on Skype to family abroad too. I don't notice any slowdowns. It only slows down when my brother is downloading DLC or a game and I want to download something.
Fibre always and forever. Though whilst Virgin Media market themselves as the fastest, or on average fastest in the UK. if you are in an area which has been oversold be prepared for nothing but headaches. BT Infinity for the win.
Then just get the uncapped package. Not sure what I pay but it's truly unlimited and crazy fast. All we need now is the legitimate sources of media to catch up on ease of use, quality and reliability to the shady sources and I'll be in win city.
That's usage My m8 got his giff gaff sim cancelled after tethering his pc to it and using 9 gb in 2 days ( they said unlimited internet access after all ) lol Iv only every had fibre with VM, so cant say anything about other providers, but iv never had any probs so far. Just look about for the best deal