Both machines are running 8 core AMD Jaguar APUs, with 8 GB RAM. The difference is in the GPU part of the APU, which I can't remember the numbers, but each has it's trade-offs. What I do remember is my buddy who headed up the chip design at AMD saying that Microsoft ordered their chips quite a bit earlier than Sony, which played a part in the higher price of the Bone at launch. So yes, the machines are just weaker pc's, but that's common knowledge. The attraction comes from the plug and play aspect of a console vs. a pc as Smoke said. The average 'gamer' either doesn't have the know-how or the inclination to mess with pc gaming and doesn't mind sacrificing shaders, textures, and frame rate (unlike Stuart) for an easy and accessible experience. Don't forget that price is also a big factor, as a decent gaming rig will tend to run between $1100-1300 (CAD, fuck if I know how much cheaper parts are in USD), vs. the 400-ish that the p4 and Bone cost.
As the other guys mentioned, exclusives don't make financial sense in the current development landscape, although there will always be those companies who either can't resist a huge payday up front or need it, like Capcom with the upcoming SFV PS4 exclusive, and Square Enix with the Tomb Raider XB1 exclusive. You'll have to be patient for the first/second party/in-house games.