Hi Vijay Singh,
You definitely know how to start a big big fight and watch the fun !!!

Well Jokes apart, Seriously speaking, it depends upon application to application, what exactly is required in the end product. Selection of Micro comes after many of the following considerations:

1. What will be the environment in which the end-product will be used. Do you need any certifications, or the class/quality of the product is specified? Do you need certifications for the product: UL, CE, etc...
2. What is the Price Tag of the end product. Calculate the approx. cost of electronics involved. There are a lot many things to consider when developing a product. The cabinet, electrical connections to/from the product, Front panel of the product, whether requires IP protection...etc.
3. After calculating the cost of electronics, calculate the cost of supporting peripherals and features that are required from the electronics.
4. Then you come to the selection of the processor.

After you have done the above, then you can ask "Which of the above is better." Have you done the above?

Points to consider when selecting the processor:
1. What are the peripherals that are required in the CPU?
2. What should be the cost of the CPU?
3. Can you go for a high $ CPU that has integrated peripherals?
4. Do you have the development setup for the CPU? Compilers, debugger, Device Programmer,...and most importantly..Do you have the trained staff to do the job?...or you need to get it outsourced or on contract.
5. What is the availability of the CPU in your locality? Is it a running product? If not, then there is a likely situation where the supplier will raise his hands and tell you that you will have to wait for the next 6~8 weeks for the shipment to arrive.. Don't be at the mercy of the supplier. Can you have alternate sources of this CPU?


The above are just a few things that popped up my mind. I might have missed a few things.....

The point is that you: From my experience, All CPU performances are almost the same. It depends upon YOU, how you use it.
You can do many things with a knife...Cut vegetables or kill a person. It depends upion YOU.

As far as I am concerned...I like MCS51, you have many flavours, from many manufacturers. Whereas PIC has many flavours, but only one company that manufactures it. So I am more inclined towards MCS51.