I think NULS definitely has that potential. Smart contracts are on the test-net already, and will be out in October on the main net.

NEO has some limitations that NULS does not.

The delegated Byzantine fault tolerance system poses problems for NEO, since if just one validator node goes offline, the entire network goes down.

NEO does not support modular chains or pos/pow modules to provide interoperability with other chains and NULS does. This article is a good read for more information: https://medium.com/@Burger_9885/the-new-kid-on-the-blockchain-3-0-scene-nuls-vs-neo-85ef73ac4ac9