TAS or M&A advisory - Big 4 firm

Hi

First let's begin with the differences:

In TAS, you are mandated during the process of a M&A deal toperform financial due diligence, that is to say in-depth investigation of the financials of the target. You check the quality of earnings, try to establish normative working capital, adjusted EBITDA and net debt of the target, to confirm the accuracy of the business plan and the valuation.

In M&A advisory, the work is actually exactly the same than in an investment bank. You advise your clients in selling or acquiring a subsidiary/company and guide them in the process.

I would also add that the Big 4 are the leaders on TAS, and you generally have one them in every large deals, whereas in M&A they basically do only small or mid cap transactions.

That being said, even if you would work on higher profile transactions in TAS in a Big 4, I would rather take the M&A role if your goal is to break into IB, since the experience is more relevant. For non IB career I would also take M&A which is a more complete job, while TAS is kind of advanced accounting. 

As for the prestige question, I may be mistaken but it seems to me like the 4 ones are all the same.