1070 have more option for sure, with amd you are stuck there mining ETH,if ethereum sink what you will do with amd gpu? nothing, there is only monero which is not profitable, other algo are not optimized or the optimization is private
you have got your information wrong, with amd you can mine any coin, not so much with NVidia as there is ONLY a small handful of profitable coins along with optimized miners for said coins, the rest AMD still dominates. sure you can mine just about any coin with an NVidia but it doesn't mean its going to be efficient since miner code for a lot of coins when it comes to NVidia are not optimized much or at all, with the exception of a handful of coins like zcash. take ETH for instance you can mine it with NVidia but doesn't make it good, as matter of fact most of the time you get much worse of hashrate with NVidia on eth than say an rx 480, if what you were saying had been true there would be WAY more people mining with NVidia than amd which is not the case
I'm not sure where you are getting this? Nvidia is better at Skein, LBC, Equihash, Lyra2rev2, LBC, and Neoscrypt. Literally the only thing people are doing with AMD is either solo-mining some Ethash coin like ETH, ETC, UBIQ,etc. The only other option, which is the better one, is to dual mine with ETH+Sia or ETH+DCR. (or something similar) Really AMD is the limited one here and I think you are like 3 months behind in thinking. Also if you are thinking about resale value then of course 1070's , 1080's, and 1080 TI's are so much better that its not even worth comparing. Nvidia cards are also easier to work with and don't require BIOS changes. Nvidia cards are also far more available and it will be a little bit before the next AMD batch comes out for sale. Really the only two things AMD has going for it are that they are cheaper, at least when the cards are available, and they have a slightly faster ROI. Even though Nvidia cards ROI slightly slower a rig with 1070's can ROI in 60 days and a 1080 TI rig can ROI in about 75 days. To me it is worth the extra expense and the slightly longer ROI to get all the benefits that now come with Nvidia rigs. I was planning on building another rig with 1070's but now that I have done a bit more research I will build a 6x 1080 TI's rig and at today's prices and difficulties that can bring in about 95 dollars a day per rig. The AMD rigs with 570's are half the price but are bringing in about 44 dollars a day. You do the math but to me this seems like a no brainer at this point. Just to be fair I have AMD rigs and Nvidia now but at least for the forseeable future I will only build with 1080 TI's.