Dell M1530 (T7500) & Vostro 1500 (T7300) do these benefit from PC-6400 (800Mhz) memory? or is it better to got for PC2-5300 (667Mhz) memory?
Looking to get 2x2Gb to take system up to 4Gb. (I know with 32-bit I'll only see between 3.25-3.5Gb)...
All info welcome before I make my mind up..
Looking to get 2x2Gb to take system up to 4Gb. (I know with 32-bit I'll only see between 3.25-3.5Gb)...
All info welcome before I make my mind up..

do you have a link that confirms this?
Just stops average Joe getting confused as to why his computer has 3.2 GB of ram not 4 GB he bought, makes sense. IMO you won’t see much of a difference bar memory benchmarks, if you can get it at a good price maybe 
I would have thought the 965M chipset was just about the same as desktop variants guess not.