The msi wind U270 uses standard SODIMM DDR3 ram at pc3-8500 or pc3-10600 speeds i.e 1066Mhz or 1333MHz. 2x4gb kits should work fine with it, it would just be a pop out pop in type replacement. 4gb should work fine enough if you are not doing anything fancy with it though. 1333 is the best pick as any faster the cpu won`t work well if at all with it(to my knowledge) 1333 is also better for the onchip/onboard gpu as they get a slight performance boost from the faster ram.
Price anywhere from $28-$65 depending on brand you choose it from..Crucial, Patriot, Corsair, Samsung
As far as the "best ram" well some are better then others as far as warranty etc, but generally ram is ram when you are talking a given speed/capacity the difference is possibly the warranty and pricing, for me, Gskill, Corsair, Crucial, Patriot are the top makers, and generally also have the best speeds and quality control.
I personally do not know what ram is in the wind u270 from the factory and its voltage/timings etc, but the sodimm memory ddr3 is generally either 1.5v or 1.35v, Crucial suggested the 1.35v option, but both should work fine, the 1.35v should also run a bit cooler(small bit) but would end up helping the battery last as long as possible(small bit as well I think)
Last edited by Dragonstongue; October 4, 2012 at 11:21 AM.