Earlier quoted context omitted.
Yet you can expect Cable service (Kabeldeutschland/Vodafone) to be to be lossy/congested at every days peek hours. Whereas DTAG _does_ way better. I dont like it, but as others have said: Relying on transit peering will not work well once you reach certain traffic levels. Also you can get Servers from Strato (DTAG Sub) for about the same price as from Hetzner and pump your Traffic directly into a Tier1.
Vodafone doesn't just offer cable service but also DSL and VDSL, and that's rock solid. The cable service slowdowns are technology inherent. But that's a last-mile problem and not a backbone problem. Also, these providers aren't trying to use their customer base to extort money from hosters.
yet i doubt that buying from a (DSL-)Reseller is improving service quality and prices are roughly the same.