UNIX File System of Mac OS Extended?


I am reformatting a Harddrive and then installing Mac OS X but I have the option of installing as UNIX File System or Mac OS Extended...I was going to install it with Mac OS Extended but realized I had no idea what UNIX File System was...can someone tell me so I can decide?
You don't need to format the disk as a UNIX file system. I don't know what's the point with it, but you won't be able to mount the OS X disk in OS 9 if you do it. Just select HFS+ (Macintosh Extended).
what about long file names? does UFS support filenames longer than 32 characters? HFS+ doesn't. that would seem to be a big deal if you are untarring unix apps that contain longer names. any opinions?