Bandwidth quality from a carrier all depends on who they peer with, where they peer with them, the backbone architecture, and support. A carrier with no direct link between Chicago and Washington DC will likely have lower performance between those cities than someone who does. If the backbone is properly engineered you'll see a more stable network. If the company has peering at many locations with many different companies you'll also have a better chance of the data getting there in less hops and with traveling a shorter distance.
What makes BW quality better?
