Which GPU chipset manufacturer is better for 2018? It still depends on what you are mining. For Ethereum mining AMD is still the preferred GPU chipset. NVIDIA is better in terms of per watt efficiency and does better at a variety of algorithms. Since there are a lot of algorithms besides Ethash which are profitable NVIDIA tends to pull ahead. For most new mining rigs NVIDIA is preferable with the 1070/1070Ti/1080Ti being the best for density.
The best way to compare various GPU’s is to visit What To Mine. By toggling between the various GPU chipsets you can get a pretty good idea of power usage and hashrate for a variety of GPUs. The site offers other data such as live coin profitability calculations as well. It is useful but be aware many people use it so some of the best coins to mine will be ones that are not listed there.