Is there any way to short these guys or otherwise get exposure to a value decline?
Shorting a company will bet specifically against that company, in a way that both:
1. Gives you monetary gain if that specific company/stock decreases in value.
2. Puts pressure on the stock to be lower value.
Thus it acts as a correcting mechanism to the market, since just by the fact that a lot of people who have an incentive to make a correct bet on a stock declining, upon placing that bet, help correct the price downwards.
Funding a competitor doesn't act anything like that, and specifically probably doesn't give you a great monetary reward, since most startups fail (thus most competitors will fail).