Answer depends on many factors.
Who is going to support the system? If you have a contract for the system support from an outside entity, then you have to stuck to the configuration they support. They may put some restrictions on what filesystems you can use.
2) Layout (number and type of filesystems) will depend on what you need. If two partitions of 8TB work for you, it may very well be the right choice. I assume we are talking about two partitions for data, and you have separate filesystems for the OS itself (/, /boot, /usr/, /tmp, /var).
3) File size and data access pattern.
Removing large files on ext3 with default options (data=ordered) is painful. If you expect to need to remove large (hunderds of GBs) files often then either go to data=writeback with ext3, or choose xfs/ext4. The same problem will occur if you will have writers that sync significant amounts of data while there's other I/O going to the FS.
3) fsck time
o) I do not have experience with xfs fsck time and requirements.
o) ext3 fsck for 2x8TB will be problematic, because of memory requirmements. You will need RAM (certainly more than 2 GB) for it to complete, preferably a 64-bit system and a lot of time (I'd say a couple of days before fsck completes).
o) ext4 is supported on RHEL 5.6, and therefore should be on CentOS. This would reduce your fsck time dramatically compared to ext3 and should improve performance too. Personally I'd go with this filesystem, but that's because of
4) Comfort zone.
From the filesystems that do the job choose one that you are most comfortable with. If you have years of experience with filesystem Z and it works for you, then probably this is a good filesystem for you.
My personal choice?
separate /boot partition formatted with ext3. Rest of the storage made into LVM physical volumes.
LVM with two volume groups -- one for the OS, one for the data.
Leave some space unused in the volume groups, so that it is possible to do an LVM snapshot of the filesystem to fsck it without bringing the whole system down (with this big filesystems silent bit rot is possible, check for it, while waiting for btrfs to mature).
ext4 for OS and data partitions -- because it is fast, I like it and trust it.