I had some thoughts about same choice.
ETH for sure.
IOTA and Ripple are not exactly block chains. Its business adjusted centralized networks. Its easy for them to sign contracts because they are flexible in terms of features.
But it will be hard to implement i think.
Block chain is not very efficient. Its main feature is distributed consensus. IOTA has some kind of central point of failure, and Ripple ...well they have lots of nice words, but i dont know what exactly do they do.
So from business perspective its just a gimmik, any corporation would be better of with some Oracle or SAP solution. If decentralized consensus is not required blockchain is giant waste of resources.
I would say MONERO, NVO, 0x, BTS and DOGE are my top choices for investment