What Format for External Drive for Mac and PC

I bought a new portable hard drive to save images on when traveling. I have a PC for travel and a iMac running Snow Leopard for work in the office. In the past I've formatted my travel drives to FAT32 for compatabilty both ways, but now that I am starting to shoot some video, I worry that I may be exceeding the file size limitations of FAT32.  I almost always downaload from the PC to the external drive then to the Mac.  I rarely move files from the Mac to the PC with these drives.

What file format should I use when setting up the new drive the first time? NTFS? FAT32?