It depends on what arm you have. If you have the JMW 9 you must level the platter. JMW is an unipivoted arm which is self-leveled and requires a leveled platter in order to maintain the correct angular relationship with a record.
On the other hand, if you have a bearing arm, you should level the pinch (actually the arm board). Otherwise, the arm will put more pressure towards the lower end.
On the other hand, if you have a bearing arm, you should level the pinch (actually the arm board). Otherwise, the arm will put more pressure towards the lower end.