Business class service will cost more. Is it worth it? that's a separate issue.
T1/T3 are: symettrical (up and download speeds are equal). This is important if you are hosting & need to send info out, VPNs, and the like.
Different level of support - higher priority for downtime, for example.
Based on different technology, that may be more expensive for the carrier (I guess).
Higher profit center for the carrier.