hmm, i've got the G6 Real 8Gbit and i believe it is to small storage space (for me) so i would in this case choose the R4 with 2GB
also, if u want download play, choose R4 because that isn't working 100% on G6 yet...
but there are other great cards you know..? like the CycloDS EVO and AceKard R.P.G (well this is so new, that you can't really know if it will be great, but it got the possibilites there alright.)