Both coin is good to invest but they have differences because BAT use to advertisements to earn. Ethereum is more convinient to invest because most altcoin use eth for investment but of course we need to choose that really want to invest. We just need more knowlegde about that coin that we want to invest to avoid some loses.
Ethereum has already a good reputation their platform is will definitely and it's been a while in the altcoin world but the movement is slowly but surely, in another hand it is good to explore some other altcoins to invest, to put another eggs in another baskets