first windows can not format something to ext2/ext3. Windows format fat32, exfat, and ntfs, but there maybe third party software that can format it into ext2/ext3 I am sure however, it is another unnecessary step.
Second, we don't know that if N4 can be formatted into ext2/ext3. Unless there is evidence that N4 can be formatted into ext2/ext3, it is a big risk I am not willing to take, considering SGS3 can run exFat sd card right out of the box, exFat is just as good as ntfs compared to the limitations of fat32.
Greater storage is always better due to the axiom of Non-Satiation, but I am satisfied with around 10GB usable storage, 7GB for one blueray (I watch and delete immediately), and 3GB for miscellaneous files.