Reliability becomes critical when customers or employees depend on your connection for immediate responses. If your customers use your connection to access your databases or your server or the internet then reliability of your connection is critical. If your employees depend on your connections because you host the e-mail server in house or host web servers, your connections is considered critical. A critical connection can be viewed much like a life line, without which your business would be negatively impacted. Your monthly savings of having a sub-par connections will not make up for the loss in productivity of your employees or loss of customers when your DSL connections gets bogged down or cut off. To reiterate, ciritcal connections should be supported with a T1.

Many customers are extremely price sensitive and cannot afford the cost of a T1 which can be as much as 20 times more expensive than a full T1 connection. Residential customers who are most sensitive to price should not consider a T1 circuit unless then have a business reason to pay for such a circuit and cannot access DSL service. Most people don't realize that a DSL connection can be just as fast as a T1 at 1.5Mbps. The shortcoming of DSL is that it is oversubscribed. This means there is a finite amount of bandwidth available and a customers speed can drop if other customers in the neighborhood decide to use their service. SDSL (Synchronous DSL) is a business class DSL and is ranked as a higher priority than residential DSL or ADSL (Asunchronous DSL). This means it is not oversubscribed to the extent than ADSL and is subject to fewer bandwidth restrictions. In short, if price is your critical factor go with DSL. If reliability is the critical factor purchase a dedicated T1.