I appreciate all the posts but no one really answered the question about whether modern fill synthetic oils tend to leak less.

It is my understanding that once a synthetic (or any) oil has found a way out, changing back will will not stop the new seepage, hence the advice against changing to full synthetic oil late in a vehicles life that has only had dino oil.

I am also not about to try to cure the leaks in this vehicle, it not that brisk but also likely not from just the valve cover gaskets. But if they got worse with a
fully synthetic oil I would be pissed. And seitching back to my current oil, from many reports, would not return to my current leak rate.