I heard the SIAcoin is most profitable to mine at the moment. But the Etheruem difficulty is still rising.
It's not profitable at all. I mine it using claymore's miner while dual mining, but just mining Sia alone is a waste. 1000 Sias are worth 0.52cts currently...at 1.4Gh/s, it takes me 2-3 days to round up 5000 of those, def not worth it, only if you have free electricity maybe.
However, once Sia get their software a bit more user-friendly and do some more advertising, they could become the new dropbox and be worth a lot more than now. I personnaly keep my Sias for the time being.