What is the best device to stream Xfinity on a TV?

In talking to Xfinity, they suggested I use the streaming app on a TV to avoid some of the cable boxes we have.  There is one TV we don't use that much so I might consider this, but the builtin Roku on the TV was pretty slow and I miss having the numbers to type in the channels.  Does anyone recommend a better option (a Roku or Firestick or something) instead of the builtin TV app, especially one that might have numbers on the remote?  Have you found it as fast or almost as fast as the actual cable box?