In the book Game Coding Complete, 3rd Edition, the author mentions a technique to both reduce data structure size and increase access performance. In essence it relies
Visual Studio is a great compiler when it comes to optimization. However, bear in mind that the current "Optimization War" in game development is not on the PC arena. While such optimizations may quite well be dead on the PC, on the console platforms it's a completely different pair of shoes.
That said, you might want to repost this question on the specialized gamedev stackexchange site, you might get some answers directly from "the field".
Finally, your results are exactly the same up to the microsecond which is dead impossible on a modern multithreaded system -- I'm pretty sure you either use a very low resolution timer, or your timing code is broken.