I would go with ethereum. Right now a lot of the ethereum projects such as ethereum name service are in the beginning stages, it is versatile because of its own programming language with a lot of utility and I think a lot more gambling sites will start switching to Dapps to assure users their gaming experience is fair. Just seeing the number of ethereum blockchain games that keep popping up on steemhunt shows me ethereum is becoming mainstream.
Steem is great but I earn steem. I invest in what I think will get me the greatest return.