Oh, what I meant was, 9400m G has the northbridge, IO controller, gpu in one chip, allowing smaller footprint, lighter and better power consumption...or something like that.
I thought that was the big deal with the new chipset.http://www.nvidia.com/object/product_geforce_9400m_g_us.html
The 9300 you mentioned, only refers to the gpu, and seems to require separate chips for the IO, etc..
I see what you meant that they'd probably perform the same. But the 9400 seems to promise a thinner lighter machine while keeping the same gfx capabilities.