Altera Stratix 5 versus Xilinx virtex 7: Which one to use

I am really unable to decide which one to choose, and which not. It is very confusiong, and the main target is to develop hardware system interfacing with the FPGA as central core processor. If someone can suggest, it would be really great. I would like to give support from the user community as the maximum weight-age.

If the FPGA will be the central core processor then why not look at the Zync family from Xilinx? In that case you'll already have the ARM and FPGA logic to add all the rest of the system "glue".

Need a better description of the requirements to give a more informed answer. In general you should really consider the architecture of the design that will be implemented and the number and size of memory structures required. After you've determined that, then look at the number of peripherals and the pins required and the type of pins to see if you have enough I/O banks to place the design in the part(s) selected. If there is any hard-IP blocks in the FPGA that you will require and the number of them (e.g. PCI endpoints). Take a look at the vendors library of soft IP and if there are blocks you need that don't exist in the other vendors library that might sway the decision. Look at the number of transceivers and their speed if required in the design. Look at the number of supply rails required (Xilinx has traditionally required less total number of different supply rails than Altera, not sure about Stratix V).

I usually build a spreadsheet with all the requirements for the FPGA and an estimate of the logic resources with about 60+% padding to account for feature creep (unless you're lucky enough to have a requirements spec that is set in concrete).

That should give you some ideas to start with.

Regards