I somewhat believe that if you're doing 3k intervals in a moderate climate (not too hot, not too cold) and don't drive very hard, that you'll see identical engine wear numbers using a conventional oil compared to a synthetic.
Synthetics main benefits come with the ability for better flow in extreme cold and the ability to last for longer intervals. They also won't thin out as easily in the long run.
Also, most people I know end up trading their cars in long before they'd ever reach high enough mileage to need an engine rebuild, so from a practical and economical standpoint, the benefits of synthetics don't show up for a lot of people (especially those that continue to change the oil every 3k anyways)
I like synthetics not only for the fact that it gets down to 0F sometimes in the winter here, but also because I don't want to be changing the oil more often than I have to, since I take care of changing oil in 4 different cars (mine, my wife's, my mom's and my sister's)
I truly believe the synthetic vs dino oil argument will never truly be solved, not as long as there are people out there going 300k while using conventional oil. Try to convince these guys that they should've used synthetic! Not gonna happen!