Actually, Apple gets first pick and only the top binned CPUs. Been that way since they transitioned.
So, generally speaking, your MacBook Pro will have a slightly better CPU in it than the competition most times.
Macs -are- still more expensive than their PC counterparts, but the "Apple Tax" of the past is by and large quite a bit smaller. It used to be youd pay 300-400+ or more for a Mac specced similarly to a PC
These days its 100-200 at most, for spec-equivalent and quality-equivalent PCs. When you look at an iMac, you have to consider the price of the display; when you consider that Apple uses top-end displays for the most part, its hard to find a spec-equivalent PC + a monitor of the same caliber for much cheaper.
That being said, particularly in laptops, you CAN get PCs that are quite powerful for less than a MBP - it wont be as light, have as good of a display, or be of the same build quality, but it will still be powerful.
If you want a completely spec-equivalent machine, though, you can expect to pay almost as much as the MBP.
Macs have two advantages to me (and is why i still use one for my daily driver despite having a powerful gaming PC sitting right next to it)
the first is OSX - its a very secure, stable, and easy to use operating system. Its also extremely powerful and versatile if you are a tech geek because it is, at its heart, fully-fledged UNIX and the command line can be a powerful tool. Also, because Apple only has to code OSX to run on their own hardware, its almost always more reliable, and faster, than Windows on equivalent hardware.
the second is the fact that a Mac can still boot Windows (and Linux) or run it (extremely capably) in a VM. Most PCs (unless they use very specific hardware and can be Hackintoshed, which comes with its own share of issues) cannot do the same.
For a "casual use" and photo editing/creative use, i'd recommend the Mac, particularly in a laptop. The quality is high, ease of use is high.