If you want to buy a smartphone based on the fact that it has 4 ARM cores, you are buying on specs, not on actual delivered capability, and those extra cores may very well be eating up more power and more die space for no reason. (I'm not talking about Moto X's low-power DSP cores, I'm talking about having 4 Krait or ARM 15 cores)
GPU cores are different because GPU workloads are automatically parallelizable, but then again, you only need as many GPU cores as it takes to drive average workloads at the given pixel density. It makes no sense to include enough GPU to render a game at 250 frames per second. Developers are most likely not going to spend time optimizing a game for a high end GPU like it was some kind of console in a fragmented market like Android.
Point is, one should look at these phones from a practical standpoint and ignore the spec sheets. Does it take good pictures? Does it feel fast? Does the screen look good? Does the battery last long? Does it feel good to hold and lightweight? Does it do cool stuff that makes you more productive, etc.
If you buy phones on spec alone you may end up with a POS that looks good on paper but is irritating to use.
Take the Galaxy S4, sure, on paper and benchmarks (some of which are cheats), it looks great. But how often are those peak rates hit? How much Android software really takes advantage of the full power of the device? How much battery life is sacrificed, or size?
You could say that the screen or memory capacity might be objectively better, but again, how much of a price in battery life are you paying for those displays?
Also, on customization, consider that Motorola is going to build and ship, to you, a phone in 4 days. Maybe you don't care about any of the color options, but you have to admit, being able to assemble and ship a phone to you with a 4-day turnaround is impressive and is a manufacturing capability that is sure to useful for other things in the future.