"The proof-of-work algorithm, CryptoNight, is AES-intensive and "memory heavy", which significantly reduces the advantage of GPU over CPU." https://en.wikipedia.org/wiki/Monero_(cryptocurrency)
Does this mean that it is generally more profitable to mine with a CPU? If I buy a new computer to mine, should I focus on CPU specs and ignore the GPU?
The most profitable consumer-grade hardware that I know of is the GTX 750 Ti (an nVidia GPU). This is on a Hashrate per Energy Used basis, since the marginal cost of mining is the energy spent. It gets ~250 H/s for ~35 W. Some intel CPUs can get ~200 H/s for ~45-60 W, so CPUs aren't at that much of a disadvantage. GPUs tend to be cheaper, however, and you can use 4-6 GPUs in a single rig, whereas consumer-grade CPUs are 1 per rig generally. So there is less "extra" cost when GPU mining in building out the rest of the rig's components.
That statement does not mean that CPU mining is generally more profitable than GPU mining. The emphasis should be on significantly reduces. The large memory footprint of CryptoNight is a large reason for this.
CryptoNight offers only a relative advantage of CPU mining over GPU mining. Which is best for you depends on your energy costs, use of the CPU and GPU for other purposes and budget.
it all depends on what you have available in cpu, low core count cpu's generally arent that profitable, high core counts are better at that.
my miner is currently running on cpu only ~2KH/s ( dual socket E5-2697v4)
the other miner with GTX970 runs at ~250H/s while the i7-6700K 4Ghz runs ~250H/s
~2000H/s 450W measured power consumption
~480H/s GTX970+i7 350 W power consumption
~150H/s Quadro K2000 80W
other numbers to be posted. project on test : 244 core XeonPhi (1.1Ghz )
