[derefr]

The difference is that ETH1 will bridge to ETH2 in the future, and therefore by choosing ETH2 as your substrate, you’re predicting that transaction costs for sibling-transactions crossing from your chain to ETH1 will become cheaper when that happens.

A similar promise cannot be made for any other substrate network, as ETH1 isn’t going to bridge to any other substrate network.

Since it’s not like sub-chain mainnets can pack up and move house after they’re launched, when launching one, you have to make choices based on how things will be, rather than how things are. It’s sort of like choosing a city to build a corporate headquarters in, based on what the civic infrastructure is likely to look like in 20 years.

[jkilpatr]

There are bridges to and from Ethereum right now. I use them every day because I need a fast sidechain for my application.

Choosing ETH2 is predicated on the assumption that ETH1 will be bridged more cheaply and easily than existing bridges can provide and that the opportunity cost of waiting is worth it.

I had to make that decision personally, decided I can't wait for ETH2, so we're using a bridge that's available today and building an ecosystem elsewhere.

Several other product leads that I know are making the same decisions, they can't just put their lives on hold and trust that ETH2 will solve problems for which there's no public timeline or even a public solution.