First off, Cable has way more bandwidth than that. With DOCSIS 3.0, you can aggregate 6 mhz channels to form a downstream pool, up to I think 8 and using the maximum modulation (256 QAM), you can reach over 300 mbits/second of bandwidth for a single downstream port which covers a neighborhood usually. Using Cisco equipment, you will have 6 upstream ports per downstream ports ( they use narrower than 6 mhz channels, around 1.5 mhz I think and can't use more than 64 QAM for modulation because then the CPE would require more advanced hardware that isn't cost feasible at this point).
Second off, the DSL "advantage" you list is laughable, a marketing gimmick. Sure your "last mile" bandwidth is all yours and dedicated, but what do you think happens once you reach the DSLAM ? From there on out, it's all as shared as the bandwidth on a cable connection, and heck, there's more people on a single DSLAM than there is in a neighborhood sharing that 300 mbits/s aggregated channel.
Both are as shared as one another, to think any has an advantage in congestion management is wrong. If the ISP has its stuff properly setup, neither solution will ever see congestion on the last mile or within the ISP's backbone.
Yes, I did work for an ISP quite some time ago.