The most speeds.
"We’ve consistently offered the most speeds to the most homes"
Since it's Comcast, god only knows what they mean by that. Comcast probably doesn't, and wouldn't admit it if they did.
Perhaps they are being literal, and they offer the largest number of tariff options. There's a long tradition in advertising of bragging about stuff that's true but doesn't matter (it's even better if it sounds like it matters).
Perhaps they mean they offer higer speeds than their competitors. In most Comcast markets, they offer up to 20-30Mbps. The competition is almost always the local phone company flogging ADSL that maxes out at 3-7Mbps).
I've been a Comcast broadband customer for a few years, and they do a decent job of shifting packets to/from the internet and seem happy enough to let me use my own mode. But, nobody in their right mind would depend on them for email, DNS, or anything else.
Where I've live, we've got a third option: municipal WiFi, but it maxed out (theoretically) at 3Mbps. I tried to use that for a few years, and it was miserable. It worked (mostly) in one neighborhood I lived in, but typically ran at 1-1.3 Mbps. After I moved to a different neighborhood, it often didn't work at all in the evenings.