I’ve moved from DSL Extreme 6000/768 service to Cox High-Speed Internet Preferred 12000/1500. Here are some comparison stats.
These tests are from speedtest.net and Visualware’s VoIP test. Unless noted, I used Los Angeles servers, and all tests route through a local Cisco gigabit switch and a Netgear FVS318v1 firewall/router.
DSL Extreme
Pretty good for a 6000/768 line. Note the low 19ms ping.
Very low jitter and no packet loss leads to a “Radio quality” VoIP score.
Cox
Cox speeds varied the first day but have stabilized at around 6.5 down. The 3.2 upload is over twice the rated speed. At 33ms, ping is a higher than DSL Extreme but still pretty fast.
Jitter seems to vary a lot, testing from 1.5 to 3.7, always with no packet loss, and always in the “Standard quality” VoIP range. Time will tell how VoIP sounds subjectively.
Cox Direct to Computer
In fairness to Cox, I should mention that its speeds are much faster when connected directly to a computer. The average is over 10 down (testing against a Dallas server), and occasionally speed spikes to 25+ (probably due at least in part to Cox’s PowerBoost® feature):
As best I can tell, the bottleneck here is my old Netgear FVS318v1 router. The specs on its WAN port are only 10 Mbps, although the Cisco switch reports a 100 Mbps connection. According to posts like this one, even the later FVS318v3 with a 10/100 port still only does 12.5 Mbps from WAN to LAN. A more powerful router with a WAN-to-LAN throughput above 30Mbps would probably yield much faster results through the router.