There is no best buy, there never was, it's all about managing the risks and calculating the overall cost. With amd cards you're mostly stuck with eth and cryptonight, and right now they're doing very well, but no one knows how they'll be doing a few months from now. The advantage of nvidia cards is that they are efficient at many more algos. The question between "more of the smaller cards vs less of the powerful ones" also has no definite answer, it's mostly down to the price of the slot and the total number of cards you manage. There are just no simple answers to complex questions. None of the 5 cards in the list is a bad choice.