Max,
I've not had any issues with my Comcast phone. Personally I am not a big fan of Comcast, but when I was deciding At&t deal breaker for me was the extra $7 per tv for boxes. Having several of the, it added quote bit to my monthly bill. Typically Comcast will give you 3 free.
Comcast internet is faster of the two.
Best of luck.
Regards,
Jeff