Well the only thing I can tell you is the most basic thing:

EXT3 and ReiserFS are both journaling filesystems. This really helps to keep file integrity.

Cool

But which is better? Ext3 or Reiserfs?

That's subjectional, meaning, it really is up to you. If it were objectional, well then there would not be this debate. Objectional meaning hard corps stone cold factoid evidence that one is better. Either by well known and generally accepted benchmarks, or by actual "Test of time" facts. Reiser has been out longer, so one would say it's had to time to work out it's "bugs". Ext3 is simply ext2 journaled, so one would say that it conforms more easily, and has been around even longer.

I use ext3 simply because it was the first journal I used.

Cool

I use UFs on my BSD box and XFS (because of ACL support) on my suse box and laptop.