Nothing makes me think 2 is -better-, just that I see more "V2 is better" type arguments.
nfsv2 as a protocol is in most respects not "better" than v3. However, most vendor's v2 code has been around long enough at this stage so that their implementation of nfsv3 is quite often not as good/stable/fast/whatever as nfsv2.
Some people object to nfsv3 because certain operations cause the server to execute stat() on the file being handled at that time. This can lead to measurable performance differences between the two protocols.
otoh, v3 can handle files > 2Gb; it can use larger read/write block sizes and it has a bundle of other fixes for various v2 protocol problems.
You should probably have a look at rfc 1813 which among other things give a brief comparison of the main differences between the two protocols.
Nick Hilliard Ireland On-Line System Operations