Surely one would also have to consider throughput, latency and other information theory preoccupations. You may get a burst capacity of 78 Mbs over 5 seconds, but how many ejaculations can the average man reasonably be expected to have over a period of, say, one week? I would suggest that even with a John Holmes type, the cable modem will win out in terms of throughput over a sustained period.
As regards latency, well, this would depend on how you measure it, but it might be fair to say that you could be looking at a lag of nine months.
I won't even get into the surely unacceptably high level of packet loss.