A lot of people here are against doing formal bitcoin business in the United States, which is where Coinbase is based. So just be aware of what recordkeeping may be happening if you transfer ETH to a Coinbase wallet and then withdraw that ETH to USD. Personally, I don't think it's that big a deal if Coinbase doesn't know how much you paid for your ETH (or BTC) and how much gains you have. It's the capital gains and income that the US Government wants to tax, hence the recordkeeping from Coinbase.
If you want to go a similar route with without the recordkeeping check out Circle.
https://www.circle.com/en. The same services as Coinbase, without the spotlight on them.
Cheers!