Whatever you do, if you purchase an A or P fare ticket, keep a screen shot showing the lowest coach fare that you could have obtained on the date of purchase.

In the event of IROPs, if you end up in coach on your A or P ticket, and if you press for refund of the fare difference that you paid, you may be offered the difference between your A or P fare and the coach fare that is available on the date of travel... which, obviously, could be much higher than the coach fare you passed up to buy the A or P.