PPS used to be good for mainly one thing: clearing waitlists on SQ. Now that the flights are no longer that full, this benefit is no longer that useful or necessary.

Other benefits are minor: shopping vouchers, luggage tags. Upgrades are rare for PPS anyway, and even more rare now due to less crowded cabins and thus no need for op ups. Sometimes you are greeted and treated better when flying Y.

I would not spend extra money to get PPS. (*G is worth more, due to lounge access and other benefits, but you don't need PPS above and beyond *G status from any *A carriers.)