You can't quite compare both of the cryptocurrencies since it has a different POW algorithm. So, it doesn't work that way.
ETH is theoretically attackable with standard hardware. This is impossible with Bitcoin. Both consume almost the same energy. I see no advantage in ETHash.
I also heard that currenttly, here is also fork ideation of ETH that will keep running on PoW.
This will be ETH Classic I think. But it inherits the poor mining algorithm from ETH.
Do note that, the power expenditure in which generated on other cryptocurrencies is surely a different thing in terms of security for each of them.
What would be a fundamental objection to mine ETH via merged mining together with Bitcoin? Thus, ETH does not consume additional resources as long as the difficulty is lower than that of the Bitcoin chain. Above all, it would be much safer. Or am I missing something?
I don't think Ethereum Classic is as centralized as ETH, but not sure. DOGE is merge mined with LTC because Jackson Palmer was the creator and only dev of the project. He wanted to quit and not compete. Cool to get both if you mine, but I don't think the community would move together. People are paying $1000 for miners that make $5 per day; they will want their ETCHASH investment back.
Many of these miners end up simply using graphics cards. What little specialized hardware there is will disappear from the market as soon as the main project goes PoS.