Have you checked out the Steve Hoffman Music Forums? Much discussion about the best sounding versions. The answer would probably be the first pressing from the country of origin, Britain in this case. Unfortunately they would cost a fortune if you could find them. Next would be first pressings of another country, like the U.S., Germany or Japan.
The recent Beatles in mono on vinyl seemed to be very popular too.
The recent Beatles in mono on vinyl seemed to be very popular too.