Not really a fair comparison, (1) Ether has a finite supply and they have not decided how many coins they will print (it is "an area of active research" ), and (2) they gave themselves a bunch of coins on day zero ("12 Million.. were created to the development fund, most of it going to early contributors..") and (3) they crowdsaled the rest of it on day 1... Grin isn't doing any of these things.

(quotes from https://www.ethereum.org/ether )

Not true. There's a time bomb in the Ethereum protocol that makes mining more difficult over time. This slows the issuance (and the whole blockchain).

During Ethereum's life, the block reward has been reduced, and the time bomb has been delayed. This is in itself an example of how blockchains depend on an initial human consensus. The Ethereum Foundation is overseeing Ethereum's monetary policy, and the miners mostly approve of it. This is not a bad thing (decentralization != anarchy).

The time bomb has nothing to do with issuance. Its stated purpose is to force the chain to go to POS, but they simply fork it further in the future every time it comes up, and the miners can (and should, for their own profit) continue to do so forever.