Personally, I favor Ethereum due to its first mover advantage. It will be difficult for Lisk to overcome the network effect that Ethereum has already built up. But competition is certainly a healthy thing which will drive innovation in the smart contract space. Perhaps Lisk will end up being Ethereum's Litecoin (although some might argue that Ethereum Classic fills that role now).

I have a small investment in Lisk which I've been holding for a while, on the theory that people who missed Ethereum's rise might pile into Lisk instead, especially given its attractive lower price point.