I'm not aware of any common filesystem that provides "data consistency" in any coherent sense, unless you do weird things like mount -o sync. Speed is too important -- Stephen Tweedie didn't make data=journal the default, either. At most you get guarantees in particular situations -- e.g., both ext3 and ext4 guarantee that a rename will not be committed to disk until writes to the file being renamed have been committed to disk. They even both try to guarantee that programmers who do horrible things like truncating the file and *then* rewriting it are somewhat protected from their incompetence.
But maybe there are other cases where ext3 does better than ext4. You must have some excellent ones in mind to lump ext4 in with tmpfs... can you give any examples?