I had comcast mega blast for years, and the service dropped all the time, although down speed high, upload speed struggled often. After 3 outages in a week, an ATT sales rep knocked on the door, I said I don't have time to buy today but come back tomorrow and it will be your easiest sale.
I'm on the ATT giga fiber now. Iphone 7 will do 350 down and 350 up over wifi, consistently, sometimes as high as 375. I'm using an old router, intend to get a new one and expect speeds to increase. So far reliability has been flawless over 2 months and 4 days. My neighbor has a much nicer PC than mine but still several years old and he gets 990 down and 990 up hardwired. my pc only has a 10/100 port.
at the price i'm paying two year promo rate of $70/month, discounted from $99.99. This is bundled with my direcTv, so not sure if that's the promo or if its just a running deal. Either way cheaper than comcast biz, and i was paying 92$ a month for mega comcast.
Comcast support blows, IMO.
hope this helps