SAP to SAP integration and PI

Dear Experts,

Reiterating the old discussion, what is best to use (PI+ALE) vs ALE for SAP to SAP integration? I am analysing if PI use for SAP to SAP integration (mainly using ALE for long) can do some good.

I understood there are certain benifit at least from architectural point of view to use PI for SAP to SAP integration in a complex landscape. Use of BPM, Central integration and monitoring platform, Lose coupling of SW systems, SOA complient etc, etc.. Can someone here give me some reason against these thoughts?

How much of interface performance is to be scrificed if we use PI in between? and how worth is it to add another point of failure (PI) in compare to benifit mentioned above?

Is there any other argument against or for this discussion?

I am sure many of the PI consultants had to go through this question. So I am hoping to get some good argument and is much appretiated.

Regards

Suman.