It depends on what applications you're using the bandwidth for. By the way, 1.5 up/down is actually a full T1 (rather than fractional).
If you need real-time traffic, e.g. reliable transmission of VoIP, video, or Citrix type applications- Then a T1 or other commercial grade bandwidth (such as carrier Ethernet) is a better option.
For general web browsing, email, non mission critical usage: DSL/Cable may be a more economical decision. Keep in mind that if you're in area prone to natural disaster, your DSL/Cable line will be one of the last things to get back up and running.
If you need a quote for either a different T1 carrier or DSL/Cable, please post your location info here:
»ISP b2b etc
(pricing and availability is all based on location)