Excellent question!
I think it should be based on the market, the most efficient and the one who solves the most problems is more valuable.
Value is thus based on meritocracy and the magnitude of problem it solves, like if litecoin is used by 30 million people and x-coin is used by 5 million, than litecoin would be more valuable. That's what I think, but I can't claim to know what's the best system.
And you're right, it is intriguing :)
Thanks for the great comment!