This depends on your budget and region, if your audience is from USA then pick up a server in USA, if in EU then EU. There isn't really "the best" every provider has their pros and cons in which you should ask them or read their ToS about the port usage/guarantee.
Unmetered is a metaphor, purposefully ambiguous, to indicate relaxed hosting thresholds; it rarely means unlimited!
Interserver does 1G unmetered for an additional $200 and $10G unmetered for $800. But, hey, at least they are honest. This sounds about right to me.
I offer 10G Unmeterred too. My data center will effectively double my bill for each server that exceeds the data threshold. I'm not paying for or subsidizing the cost of the data, so you can see the problem. This is often the point where your host will ask you to leave, which should be a tiny percentage of your userbase.