keccak seems interesting if you're already mining ethash on Nicehash, but I wouldn't mine Smart/Max directly (nowhere that I can find to exchange it thus far). I'm happy mining XVG and converting to ETH weekly using changenow.io
Maxcoin is already dead and smartcash is going that way as there is just one exchange(cryptopia) accepting it and is already delisting it. I would stay away from keccak then. I really don't know why claymore added keccak though to dual mine, maybe a very secretive coin is using keccak hehe