You get the satisfaction of knowing exactly what goes in your computer. Big Computers will sell you the cheapest thing for as much money as possible You dont get system warranties cause you put it together. When something goes wrong on something you built, you can call tech support (you) and place yourself on hold if you wish. Cyberpower/Gateway/Dell however flimsy and crappy they may be, usually have a warranty. When something goes wrong, you can call them and speak to "Bob" or "John" and have your call recorded for training purposes. Mac's dont have warranties, because Macs are Perfect and its you who failed to operate it correctly . You also have to provide an OS. There's also obsolescence. Big Computers dont want your computer to last forever. They arent as expandable, because that would be counterintuitive to making money. You however can plan a build with some futurproofing. Extra ram slots, more sata connectors, yada yada yada.
FWIW I like your build. Your PSU is great for a single card, but if you do plan on CF someday, you might wanna consider at least a 650w