+ 0 Votes Actual mileage may vary robo_dev 3 years ago In theory, a ADSL or VDSL link will be much faster than a T1, but there is an important physical difference. With a T1 you get a dedicated port so that your bandwidth is predictable and will not vary, with a SLA to back it up. Thus you pay more, but the uptime it guaranteed and predictable, if not as fast. With most DSL circuits, you are in a DSLAM with all the other DSL circuits, and you are competing for bandwidth with the other DSL users. This can make throughput less consistent depending on what the other users are doing. Plus as a 'cheap' user, the SLA is typically 'best effort' versus a defined maximum downtime window. A 'business DSL' circuit will typically have some sort of SLA, but typically something like 24 hours or less, while a T1 typically has 4 hour SLA. Where I live, for example, AT&T does a remarkably good job with their DSL service since they do fiber to the DSLAM for the uVerse TV service. I've seen DSL circuits with something like five minutes of downtime per year, and consistent throughput within advertised specs, day-in-day out. However, DSL depends on how good the last mile of copper is, and the distance, obviously. So if you are in a 100 year-old-building with the copper lines getting eaten by rats, and you are 25,000 feet from the DSLAM, then your DSL experience may not be so good.