Grin will be outdated once LTC implements mimblewimble.
Beam will be outdated once LTC implements mimblewimble.
ADA is being developed by academics with not a lot of real world success and they're behind on any possible schedule, their business plan also has little value for real world businesses.
I'd invest in none of them.
i am constantly monitoring the grin and beam, but thanks to yout inputs it gives me an idea to stick to the old one rather than wanting to participate in a new types of coins, but having this two coins in the port even a small fraction might br better rather than nothing.