As someone who did the exact transformation (SC in ACN --> M in DTT), I can share my experiences. I was in business consulting side, so maybe all might not be applicable:
- Biggest difference I saw was DTT is far more sales oriented and get ready to spend a lot of time in business chasing (RFP response etc). In the induction, one partner clearly said "you are all salesman now".
- Teams are smaller and the assignments were significantly shorter (more around 3-6 months), at least for business consulting side.
- Leanandgreen is right; business is far more UK centered, though UK acts like a center of excellence in the region.
- I think due to size, it is a little bit more competitive and expectations on levels are higher than ACN. Caliber of resources are good and last time I checked, there were a lot of people waiting for promotion; so be ready to working on building your network
Other things do not differ too much; still very political, still without your network you don't get promoted and most I've seen were questioning whether it was worth the effort yet working towards a personal goal (leave after X years, leave after Y rank etc).
Good luck in your negotiations!