I merely tried to point out that discussing "specific advantages" in detail is rather pointless. If the PIC is the best for your app, by all means use it. However, do not get into a state where you use the PIC or the '51 for invalid reasons such as "it has a separate stack", this is totally irrelevant, the only thing that is relevant is:
1) Does seleting this chip make the product match the specifications.
2) With the engineering cost divided between the units produced, is the cost of materials and development acceptable.
3) Can the unavoidable "little improvement" and the "nice little feature we MUST add" be fitted without major redesign.
and unfortunately:
4) Is this chip available with an acceptable lead time and is this going to be the case for the duration of the production run.

Erik