As far as I know neither os will read the others format without extra software apart from osx reading FAT32 but its not much use for big drives
I formatted my external drive as NTFS and downloaded NTFS-3g to the mac
http://www.apple.com/downloads/macosx/system_disk_utilities/ntfs3g.html
There is a similar programme for windows but not sure what it is!
hope this helps!
maximum disk size for fat32 is 8TB..
osx will read ntfs but not write to it without software.
OSX will read NTFS no problem but it won't write to it. So if the drive is only going to be read on the Mac no problem. However if you want to read and write to it from the Mac you need to get a copy of NTFS for OSX. It's from paragon Software. You can get a copy from the Apple shop, about £25. You can download a trial copy from Paragons web site. I did this then ordered a copy from Apple
http://www.paragon-software.com/home/ntfs-mac/download.html