Comcast is in the midst of an upgrade of all the feeder lines in Arvada to push Fiber deeper into the subdivisions both for reliability and additional advanced services. All other problems aside (and I do not know what your specific problems are be they service, reliability or price), Comcast internet can not be beat. It would be a significant downgrade to move to Century Link. The grass is not always greener as the saying goes but you never know if it will suit your purposes until you jump ship. I would only say try to stay out of any service agreement that requires a contract so that you can jump back over the fence if you find the new service lacking.
Comcast did the same in my area as well and the speeds are slower.