Your mileage may vary a bit depending on what your members do (e.g. videographers use much more bandwidth than, say, almost anybody else!).
My rule of thumb is to buy the best internet connection you can afford + a failover if it’s possible. The two things to never skimp on are bandwidth and coffee.
Two things that aren’t obvious about coworking Internet usage (and how bandwidth is just a tiny part of the equation) until you’ve had hundreds of people piping through a shared connection every day:
1) bandwidth is important, but latency is more important. Without getting super duper technical, latency is the speed that the network responds, which is different from how fast files download.
MOST people spend a lot of their day clicking around the Internet, or using internet connected apps. With some rare exceptions like game developers and video editors, the files we move around in our daily work are relatively small. Video and VOiP might seem like it uses a lot of bandwidth, but overall it’s quite small!
The problems happen when the latency is bad - everyone feels it because clicking to load a page, or refresh email, or live typing on Google docs etc feels like it has a lag. Our network (internal wireless + gigabit ethernet) used to have a Comcast Business connection of 50mb down/10mb and always had more than enough bandwidth for 120+ people working hard every day. And that includes streaming videos, music, etc. Normal usage, even with 100+ people on the network, rarely peaks above 30-40 megs down and normally idles well below 10mbps.
Where things go haywire is when latency goes up. This can happen in our network because wifi coverage is interrupted, or because our internet provider is having issues, or most often because someone on the network is uploading a huge file (offsite backup like a Dropbox sync or uploading a video to YouTube) and our ISP starts to throttle latency because it thinks something is wrong. This took is FOREVER to figure out!
We since switched to a much better local provider that gives us 250 down/150 up for a fraction of the cost, and our normal network latency compared to comcast dropped by 70% (again, lower latency is better). It’s a rough experience to explain to people, and they don’t care if it’s latency or speed they just want to work. So understanding that more speed without an improvement in latency is important.
2) the network itself is just as important as the Internet connection. You can check out my past post on speccing out a solid, reliable Unifi network for a fraction of the price of anything else on the market.
As far as Comcast vs Verizon, I have had nothing but horrible horrible horrible experiences with Comcast and will not ever give them a dime of my money again. Verizon isn’t a saintly corporation either, but I can’t say anything but good things about the FiOS service I have at my home and it would perform perfectly at Indy Hall if I could get it there (which we can’t, sadly).