Easy, higher latency on the 10Mb/sec line. The Time Warner system (at least when I spent time there) was notorious for overloaded routers and poor routing causing very high latencies.
I am not all that knowledgeable with the technical side of networking but I assume latency and ping is similar or the same (or atleast I always assumed so). Ping on my twc account always was pretty low, 15-30ms and my new verizon ping seems to be the same.
A "ping" return is only one small part and should never be used as anything other than a connectivity check. Ping in Windows uses ICMP packets, which on almost every router is given the absolute lowest possible priority (sometimes even simply dropped).