if you are asking about Bot which is will do buy/sell order i do not know which one is the best,
because they're a program and can not make a flexible movement based on market movement.
(i heard a lot of this bot programmed by the creator to make a profit for the creator,because the bot programmed by him and will processing the protocol that he made when he created it)
but if you are asking about another type of bot,i heard a bot called
GUNBOT which is will telling you a time to buy/sell.
so far i heard a lot of compliment from the traders,
they claimed get a lot of profit from following the signal created by this bot,but to be honest i never use this bot before.
for your reference go here for more information :
https://bitcointalksearch.org/topic/gunbot-automatic-poloniex-profit-generator-1715214[GunBot]
Note : Seems like it can do that type of works