im buying a desktop computer (have only a laptop). and cant choose.
I plan to buy an i5 3570k but, for gaming purposes is haswell worth ? (i will have a really good chassis and will buy really good cooling ystem for it)
If you're buying new and not upgrading from an existing 1155 CPU, then there's no reason not to go with haswell. The haswell equivalent of the 3570k is roughly 5-10% faster, and if you have adequate cooling like you say, the extra heat won't even matter.
well, it is like this - Haswell has 2%-30% /single-thread - multi-thread/ advantage over IB.
And since there are very few good multithread apps /which games usually aren't/, the general decision falls kinda like this>
for a new PC - Haswell is to be recommended,
but and upgrade from IB to Haswell is generally somehow parallel and thus generally not a good idea.
Go with the I5 4670K. About 5% faster per clock so you would have to overclock your 3570K by 200MHz to equal it in speed. Also, for applications, the Haswell is much faster with it's newer instruction set. Plus the Z87 motherboards are better and newer, more of a life time ahead.
We are finally at the point that games are starting to use multiple cores and hyperthreading. With Battle Field 4, the I7 4770K is 27% faster than the I5 4670K. Of course if you do rendering etc. the hyperthreading comes in handy too.