The gentlemanly move, and by far most common is to concede the putt and take the 1 up victory. In 15 years of pennant, I've never seen otherwise. If someone tried telling me to putt the 6 footer to see if they win 2up or 1up, I'd tell them to go **** themselves, pick up my marker and walk away.
The only time it could even be considered is in a situation like Blakey has referred to, where total holes won could have an impact on the outcome for the team.