Eth has enormously higher verification costs than Bitcoin, so it would centralize more and faster.
It will undoubtedly centralize, not sure about more and faster. I'll throw a hundred buck at it anyway in the summer when the price declines. It's hard for me to believe in one digital currency rule them all dream, it goes against rationality. What I suppose has good odds of happening is a bunch of cryptocoins in circulation, Bitcoin leading the way for some years if the Chinese don't play it rough.