I believe the OP is referring to all clubs, not just putting.
The penalty for off-ding hits depends on the playing characteristics of the club in use, including putters.
http://www.wgt.com/help.aspx#equipclubs - scroll down to Clubs
Avg. Distance: Displays the average distance the ball will travel when hit at full strength on a flat surface and with no wind
Trajectory: Indicates the general height of the ball flight
Precision: Defines generally how close to the aiming point the ball will land based on where you hit on the swing meter
Forgiveness: Displays how much Distance and Precision the ball will lose if not hit perfectly
Shot Shaping: Displays the level of "workability" of the club to move the ball left or right during flight
Spin: Defines the level of spin the club will transfer to the ball. A ball with more spin will stop faster on the green
Meter Speed: Indicates the speed at which the swing meter moves, with 5 being the fastest
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When you are looking at item categories such as Drivers, Irons or Balls, you can compare up to three items at once by clicking the Compare checkbox for the item you want to compare. You must compare at least two items but can compare up to three items. After you have selected the items you wish to compare click the Compare button to see the attributes for each club listed next to each other.