Which greylist milter is least maintenance

I am going to implement greylisting in a sendmail milter.

Which is the most maintenance free in a business environment?
One mailserver, 100 addresses, about 14,000 active customer
correspondents. average daily mesage volume of 1,200 valid messages
after removing the 92% of spam/uce.

I'm shooting for removing the additional 150-200 spam messages a day
that get through.

I'm considering:
milter-greylist, graymilter and milter-gris, and smf-grey.