The network decides everything
This is ether's main difference from other coins: it can be moved a dozen different ways, and the cost range is enormous. A transfer on Ethereum mainnet costs a few dollars; on Arbitrum, Base or Optimism it costs cents.
The gap between "a few dollars" and "a few cents" is the gap between a losing and a profitable route. Ether spreads between major venues rarely exceed tenths of a percent, and the mainnet fee consumes that entirely on any size below a few thousand dollars.
The practical rule
Before calculating profit, check whether both exchanges share a cheap common network. If one accepts ether only on mainnet while the other sends only over Arbitrum, there is no transfer between them at all — at any price difference.
The «transfer here» column below shows exactly that: whether the coin can be moved from the cheapest venue to the chosen one, and what it costs.
Speed
Ether is faster than bitcoin: mainnet confirmation takes minutes, layer twos take seconds. That makes transferring during a route possible in a way bitcoin rarely allows. But the spread still lives shorter than the transfer, so pre-funded balances remain the better method.
Where spreads are usually wider
Like bitcoin, ether is too liquid for gaps to persist. Visible differences arise during sharp price moves when venues fall out of sync, and barely at all in a calm market.
A separate case is wrapped versions: WETH, stETH and wstETH trade as distinct coins and sometimes diverge from ether. But that is no longer arbitrage on one coin — those are different assets with their own risks.
