When choosing a data center facility to colocate your servers in my opinion it is best to choose a facility that is carrier neutral. A good carrier neutral facility should have at least 10 carriers in the facility. Most data center offer several carriers on their network, facilities should offer at least 3 carriers. Five to eight carriers is preferred. Because so many carriers are in the facility bandwidth prices tend to be lower because you have so many carriers competing for your business.
I also suggest facilities that use optimized bandwidth solutions. Better facilities use hardware that monitors their carrier networks and examines network conditions like latency, packet loss and jitter. Theses hardware platforms will reroute your internet traffic on the fly is a problems occurs. Think of it as brown out protection or that quickest way to a destination is not always the shortest path.
Always look for N+1 redundancy and ask if they are using flow control or route optimized bandwidth.