PWC -> Investment Banking

I'm not really sure about PwC's Corporate Finance practice (which as the OP said is their Investment Banking group). While it's directly transferrable skill set, I would almost think working in the PwC Financial Due Diligence (QoE sell-side/buy-side advisor) would be better just because the quality of clients you would be working on are much better on the FDD side. 

Out of the Big 4, I think Deloitte probably has the best investment banking practice due to their acquisition of McColl Partners. 

I did it - was in the M&A team at PwC and moved to IB (I’m in London). It's not easy, but it's do-able

Strategy& or the corp finance/inv banking division. There are no other correct answers

As someone who has made the move, here is the order of relevance from what I heard while exploring a similar path:

1) Corporate Finance Division - just easily the most transferable skill set; easy to transfer into MM IB, harder to get into BB or EB but would still say not impossible in a good market environment, networking would help

2) Transaction Advisory Services - FDD - Not as directly transferable, but you get more comprehensive deal process exposure compared to valuations; relatively easy to transfer to MM IB, harder to get into BB or EB without networking

3) Transaction Advisory - Valuations - Better modeling experience than FDD but less comprehensive deal process exposure so gets discounted a bit; relatively easy to transfer to MM IB; harder to get into BB or EB without networking

4) Financial Markets Practice - Financial Analytics - this is kind of a slept on / not well known team outside of or even internally at PwC, but if you strike out on the other areas it is not a bad place to be. They do a lot of valuation support for the audit teams, including some PE audits. So while they don't get transaction exposure, you will get solid modeling experience; I think it should definitely be a doable transfer to MM IB from here with a good market environment, networking may help with explaining the type of work you do, as it is less well known than TAS.

5) Audit - Transferring out of Audit directly to IB is hard, plain and simple. Some people do it, but its generally because they either A) networked hard or know someone at the bank or B) got really lucky and audited a major transaction / did actual analysis on it like fair value testing etc.. (rare but does happen)