Your consultant should have wider clinical knowledge and be able to recommend strategies to improve your balance and control, some are better than the DSNs, some not (all depends on the individuals) but all work as a team.
The Consultant can also recommend and action new healthcare strategies (if you need them) like changes to pumps, insulin types, CGM etc etc and sign them off - so more power and more knowledge, but as I say it depends on the individuals - hopefully you'll get a good review and benefit from it, go armed with lots of information and ask about the things that you think might help if you don't already have them