I have been running royal since 6000 miles. I love the oil. I get it for $7 a quart through summit racing. I will not be running any other oil in the sonic as long as I own it.
On the other hand, Mobil one is a darn good oil too.
It boils down to your preference and what is easy to get.
Mobil 1 is pretty darn good for the price. Especially when you stock up when it is on sale. I used Mobil 1 for 75k miles in my Matrix. Popped the valve cover one day for some work and it looked still looked brand new. Shiny silver metal. So I say its better than Royal Purple for the cost.
When it comes to brands and even viscosity of motor oil I would compare it to underwear and socks. Some guys like Hanes, some like Fruit of the loom and I'm willing to bet some even like victoria secret but have no data on this.
Point is, in the end what you pick probably won't matter but go with the one you like most for whatever reason whether its advertising, price or availability.
Yeah, this question is very subjective and you won't get an answer to your question. In modern day, in general, oils have come a long way. Use a known brand, use the right viscosity and make sure the oil meets manufacturer specs. That's all you really need to worry about.