It depends on your budget, recently when someone I know asked me what CPU to get, he originally was set on the 6700k, but he already had a motherboard that had the socket that could support the i7-4790k, therefore he ended up going for the i7-4790k. If you have a motherboard that already supports this processor, then this may be your best call in terms of money (otherwise you will also be looking for new motherboards and maybe DDR4 RAM, unless you already have compatible RAM - DDR4-1866/2133, DDR3L-1333/1600 @ 1.35V, see
Intel ARK for more info). If you can afford a new motherboard, I would go for the 6700k.
Some benchmarks show quite interesting results - yet in most the processors are neck and neck against each other. The main difference between the two is that the 6700k has support for DDR4 memory as well as better integrated graphics (which you will not be playing ArmA on I hope...) Either one will be a great candidate for overclocking if you are into overclocking.