According to Newegg comparison the main difference is that the 3570 has the Intel HD 2500 graphics and the 3570K has the Intel HD 4000 which of course will be better.
The i5-3570 has a locked multiplier, the i5-3570k has an unlocked one, it's useful if you want to overclock the cpu.
Also yes, the i5-3570 has a different on die gpu, the intel hd 2500, the other one the intel hd 4000.
the k has an unlocked multiplier and the non-k has vt-d
as mentioned already they have different gpus as well.
even with a dedicated video card you might consider having the better igpu. quicksync on the hd4000 is considerably faster than on the hd2500 and quicksync is pretty badass at transcoding.
i was thinking about i5 3570 + sapphire hd 7870 oc or amd fx 6300 + msi hd 7950 oc twin frozr and i cant decide..my friend tell's me that amd suck other tell that amd is good i dont know what to think anymore :S
the second system is more balanced, the first system is a bit processor heavy and lighter in the gpu department. you would see more fps with the 2nd system i would imagine but the first system would still leave you room to upgrade the gpu down the line for even more fps when you need it.
I'd get the i5-3470 and the 7950 or 7870 XT.
There's no performance difference between the two i5, usually the i5-3470 is cheaper.
If you can't afford a 7950, get the 7870 XT, which is basically a 7950.
i dont think it is better, i think it is more balanced.
personally i side with getting a k processor for a few dollars more and squeezing every bit of performance out of it i can. then i upgrade the gpu every 2-3 years.
Both i5 are good ones, the i5-3570k is only worth it, if you want to overclock the cpu.
Any of those will not bottleneck the cards, by the contrary, i'd get a better gpu for the i5.
Like the 7870 xt or 7950, like i said.
It's a 7870 Tahiti LE, it has more shaders and transistors than the normal 7870.
http://www.techpowerup.com/reviews/Club_3D/HD_7870_jokerCard_Tahiti_LE/