That is a monster thread, and not for the faint-hearted.
There are, however, some real gems amongst all the white noise.
My own take on this issue has always been:
1) Whether PA and CA are covered by one, or more than one, procedure, is less important than engendering a mentality of proactivity, and not just reactivity.
2) Everyone is comfortable with corrective action and correction (yes, they may debate the terminology, I could care less as long it gets done).
3) Everyone is comfortable with the concept of preventing recurrence. However people tend to lock into this as the only required Preventive Action, which I think is wrong.
4) Companies actually do a lot more PA than they realise:
Maintenance (and planning of)
Process Risk Management
Process contingency planning
Disaster Action plans
Health and Safety schemes
Action and alert level implementation
(Arguably) training, followed by Competency Evaluation
5) I tend to recommend to my clients that they create their own list of the preventive activity that they perform, and how they evaluate the effectiveness of those preventive action processes.
Since probably every CA is probably due to a failure of PA this can be an interesting debate.
6) Part of the answer to the above falls back onto Management Review, which requires both the status of both CAs and PAs to be reviewed. Most of the places I audit only talk about the CAs (and follow-up activity to prevent recurrence).
7) The other reason that Management Review is a good time to cover PA, is because it is at these meetings that the strategic plans for the future are discussed, together with contingency planning for those plans, or decisions that extra resource is required etc etc.
I accept general evidence, minutes etc, that proactive PA is ongoing, I don't need to see complicated forms filled out.