In my case I don't remember which OS showed the most space, but I think it wasn't usable anyway. FAT filesystems are very susceptible to damage, which is why I do a full format once in a while to fix things. You can format FAT in Linux, but I tend to prefer native formatting whenever possible, given the fact that MS isn't very forthcoming whith implementation info. That said, FAT has been around long enough for plenty of info to be published. I have been reformatting my pendrives in FAT32 for a while now with pretty good results. I say reformat because, surprisingly, they tend to come factory formatted to FAT16 even for the 1 or 2 GB sizes. They also sometimes come without a partition table (like floppy disks) and I create one, though this has actually proven to be dangerous on some (mostly older) models.