There is a big misconception when talking about internet speed for end users. You can have a 3 Meg DSL and it will not necessarily be faster than a 1.5 T1. Why is that?

DSL is a shared technology. This means that everyone in a 3 mile radius or so will be sharing the same connection. The bandwidth will range during the day depending on usage. You might be flying early in the morning then slow down just as the kids are getting home from school. Also, DSL has to be regenerated through a series of pops in order to get you out to the world wide web. This can slow you down which is referred to as latency. DSL is considered a "best effort" product and can experience long outages up to 2 weeks or more. The other difference with DSL is that it is "asymmetrical" which means the download speed could be 1.5Meg but the upload speed will only be 256k. This does not work when you are sending large files.

T1 is a dedicated circuit for you alone. The bandwidth will be constant. Typically, you would want to deal with a tier 1 carrier or an Internet Backbone Provider (IBP) instead of an Internet Service Provider or ISP. ISP's buy from IBP's. T1's are regulated by the FCC for maximum uptime. T1's are "symmetrical" which means you will get the same download and upload speeds. In most cases, you can find bundled packages where you can enjoy the benefits and not have to pay more money to get it.