Do you negotiate KPIs into contracts pre or post award?

I had this question recently on a client project. From my experience, I've always felt it best to negotiate performance measures prior to contract award to ensure they are enforceable and in line with contract expectations. However, some chose to disagree, arguing it was better to determine measures of performance once the contract was in place. What's been your experience with this? And are there KPIs you always seek to include in a contract?