It is actually quite difficult to compare service providers like this without personal experience or knowing someone who has personal experience. A lot of the experts on here are UK or US based so I suspect you might not get a definitive answer.
If I can offer some advice though. I would be asking a prospective service provider about their coverage, density and availability. I would also consider my personal requirements such as bandwidth and do we need resilience at core or all sites?
If you have any other questions, please repost.