Quality of service is usually different by neighborhood. (old/new wires/fiber etc) (not customer service though - comcast probably wins the shitty customer service award)
Never had much of a problem with centurylink in 20 years here. I'm not blazing fast, but meh. I'm 50 down 5 up, DSL. Usually watching mutliple tv's and kids gaming at the same time.
Cable is faster.