To be honest, and I know this makes me a terrible salesman, but there are too many differences to list. Instead, I would approach this from the other way around. In other words, wrt your workflow and preferences, is there anything you wish SGPro did and see if that thing is offered.
That said, in terms of just a general data dump:
- Sequence Generator 3.0 is Released - Releases - Main Sequence Software
- Sequence Generator Pro 4.0.0.676 is Released for General Use - Releases - Main Sequence Software
- Sequence Generator Pro 4.2.0.895 is Released for General Use - Releases - Main Sequence Software
- Sequence Generator Pro 4.3.0.1252 is Released for General Use - Releases - Main Sequence Software
- Sequence Generator Pro 4.4.0.1339 is Released for General Use - Releases - Main Sequence Software
- SGPro 4.5.0 is Code Complete - Sequence Generator - Main Sequence Software