EY FSO vs IBM as a Senior Consultant

I have been a consultant in IBM's Consulting by Degrees program for nearly two years and I have an opportunity to move to EY's Performance Improvement practice within FSO-Wealth Management. If I stay at IBM I will promote to senior consultant this year and the offer at EY is also for senior, so there is no discrepancy.

My goal is to gain mentorship, more strategy oriented experience, and apply to B-School within the next 1-2 years. Long-term, I want to work in corporate strategy or corporate development.

My questions are as follows:

-From an MBA perspective, which is a better company to be in?
-Is there a stronger sense of community and mentorship at EY?
-How quickly can one promote from senior to manager at EY?
-What kinds of projects are most common in FSO? How much exposure to strategy work would I get?
-Any insight on the Wealth & Asset Management group specifically?

Any general thoughts on IBM FSS vs EY FSO are helpful as well.