[Exim] DB3 errors on lookup (solved); performance ?

I'm running RH7.1 and I was trying to use a DB v.3 database for address
rewriting. I built the database using the Perl DB_File module. I kept
getting messages:
2001-08-17 15:53:37 15XpgX-0000s3-00 Expansion of
${lookup{$1}dbm{/etc/patrondb/alias.db}{$value}fail} failed while
rewriting: failed to open /etc/patrondb/alias.db as a db (v3) file:
Success
After poking around in the source, I realized that dbfn.c uses DB_HASH
for DB v.3 files and I had been using DB_BTREE. I changed the flag in
my Perl script and things worked fine afterwards. (Well, I also had to
change dbm to dbmnz, but that's a FAQ.)

Which performs better for largish (60,000 records) databases, HASH or
BTREE?
Thanks,
John