Basically the trade off right now (Thanks to Intel's borderline monopolistic policies lately) is that you can either have a Core 2 Duo plus a third party chipset (like the NVidia 320M) or you can have an i-series processor and are stuck with Intel's chipset and graphics.
The only way to have an i-series processor with decent graphics is to add a dedicated GPU like the 330M that the higher end MBPs use, plus an extra chip on the board to handle the GPU switching. This creates a bigger battery drain, heat load, and requires more space on the board.
You have no idea what you are talking about.
The newest INTEL IGP peforms equal or better then the 320m.