5-10 thousand operating hours between service affecting failures, as opposed to 20,000 for the M5000's which is considered good for a tram. A class 350 has something like 50,000 miles between service affecting failures so thats what, couple of thousand hours?
A 350 can do Liverpool-Crewe (assuming it's one of the faster trains) in the time a M5000 can do Bury-Sale. However, conversely the M5000 will only be sat at the terminus for a few minutes before leaving again, while the 350 might be sat at New Street for at least 20 minutes.