Hi, can someone tell me the basic differences between the 2 cpu cards? (Mcp and MP20)

The mcp was the original card when it was released.
It only supports upto 4.46 firmware and had some feature limitations (no mobex, no encryption, less sip support)

The mp20 was the 2nd processor and has none of these limitations. Supports all firmware from 4.30 upto the latest 5.01

The mp20 is required for some cards (svmi20i, cnf24), allows the mps channels from an oas card to be used.