Here are my thoughts on how these both differ:
1) Market positioning: S& positions themselves as a pure management consulting firm and compete with MBB based on price, scope of work, etc. PwC, on the other hand, offer much more broader services e.g. implementation support along with consulting work
2) Scope of work: S& = Strategy typically. PwC = Can include many other forms of consulting e.g. Risk Consulting, HR Consulting, IT consulting etc
3) Salary: Because S& charges their clients higher fees than PwC, they also pay higher salaries than PwC. S& salaries in some regions (like the middle east) are also higher than that of MBB
4) Brand: PwC is typically seen as a Financial Services company that does Audit, Tax and some Consulting services. Strategy& is clearly seen as a MC firm, but its brand name might be stronger in some parts of the world than other.
All the best!