Its really a matter of you get what you pay for and that said, there's a reason that boards so cheap.
The B75 chipset designed for business orientated mb's. The Z77 chipset is the performance orientated chipset.
A quick easy explanation of the +'s and -'s
The z77 board gives you 2 more ram slots (4 instead of 2)
1 extra sata3 port
3x pci-e 16x graphics cards slots (instead of 1)
1 pci-e 1x slot, for sound cards/wireless/raid/etc (these can go in spare 16x slots too)
better on board sound and 7.1 support and optical sound out
Full overclocking features
Full SLI / Crossfire features
one benefit of the 3570k, apart from just being slightly better is the HD4000 graphics engine (the on board video card on the cpu) which is drastically better then all the other i5 on board gpus (HD2500's). This only really matters if you want to wait for the 660 to ship to aus
Don't underestimate your self on being able to OC, its pretty simple to get a rock solid modest overclock going, if your not trying to push the max out of your cpu. With UEFI instead of bios and the hundreds of step by step guides out there you should easily be able to get a good ~15-20% increase going. Sure it gets hard the higher you try and go and getting a stable high overclocks is really hard, but getting modest easy oc's these days is easier then ever.
Really if all comes down to how much money you got, im going to quote Barneygumball in the other pc building thread
BarneyGumball wrote:I think I might grab the K model anyway. Not so much for now, but if in 1-2 years from now, I want to get a little extra power out of it, I'm gonna be mad at myself for being so precious over $20.
It does suck to be 6months down the road with plenty of spare cash wishing youd just spent the extra little bit, me and plenty of people i know have been there