In the US, lines for T1 data are normally treated as higher importance by Telco's than x DSL lines, so time to repair and provisioning can be considerably faster. A T1 fault may be repaired within hours, or a day, whereas a DSL line fault could be a 5 day turn around time.

The other important difference is that T1 lines are more easily repeated to cover longer distances, something that has not yet happened for SDSL lines. (15,000 - 18,000' from CO)  T1 lines are significantly more expensive than DSL lines, a monthly T1 lease, with internet bandwidth, can amount to $450 or more, compare that with SDSL prices of a few hundred dollars for the same speed. Compare T1 rates.

So are you looking for reliability or price?

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, critical connections should be supported with a T1 connection.