This is really interesting to see.  Just a little background, I had installed
FreeBSD 5.2.1 on two CS20s and had them act as NFS client/servers to
each other while they continuously wrote large files on each other's
NFS mounted disks.  The CS20s are basically identical in memory and disk,
and as you'd expect the numbers for writing on each other's mounts were
fairly even with numbers between ~2070000 and ~3011000 B/s  .. slow for
100mbit ethernet, but fair for NFS you might think.

Today, I decided to give NetBSD 2.0x another shot and installed 2.0F on
one CS20 (the later with the 2.0G kernel) and continued the writing on
NFS mounts.  Besides the issues I wrote about earlier with the generic
SMP kernel locking up within an hour then nfsio performance degregation
and weird locking problems, I've noticed that the NetBSD client writes 
faster to the FreeBSD server than vice versa.  I should also note that
numbers I'm seeing from the FreeBSD client writes are a 1/3 or less of
what they were when it was writing to a FreeBSD server.

Client   Server   Low B/s   High B/s    Avg B/s   Iterations  Generated Zeros
FreeBSD  NetBSD   1118474     725269     888298           82            200MB
NetBSD   FreeBSD  1728968    3433563    2421736           82            200MB

Avg is based on the sum of all 82 iterations.  I should also note that 
although the two machines are using the same network, device type and
medium, the NetBSD machine has reported 24247 errors and has had a few
interface timeouts which could have prevented the FreeBSD client from
writing fast enough .. However, since its the same ethernet device, 
it obviously can write out well enough to the FreeBSD server.  Again,
no tweaking, just fresh installs .. so I am assuming that the writes are 32k.