Personally I am a fan of the p106-100. From my experience they have a lower power draw and slightly better temps on the models where they increased the size of the heat sink.
I haven't done extensive tests on every model/algo out there. But the testing I did showed the best ETH efficiency compared to any other GPU currently available(rx470 hynix might be better but I don't have any to test).

As for the P104-100, I don't think the eth efficiency is quite as good not to mention the price tag.

If either the p104 or p102 can show similar efficiency gains over the retail models for any of my favourite algos, then I will probably build rigs of them