What wallet size difference to expect between Bitcoin Core (binary) and Electrum (json) wallet files?

Question

Imagine a relatively big wallet with tens of thousands of addresses and 3x transactions.

Now, let's say I restore such a wallet and do full re-scan in two applications - in Bitcoin Core and in Electrum.

Ignoring the size of the blockchain itself when it comes to Bitcoin Core, and comparing only the file size of the wallet file(s), what difference should I expect between Bitcoin Core and Electrum, or, more generally, between Bitcoin Core and other wallet client software that uses json/other textual format to store the wallet data?

Answer 1

According to some people, the difference between simple binary encoding and JSON is often one or two orders of magnitude (10 to 100 times).

Obviously it depends on the data and the exact details, including indexing strategies etc. I think you'd have to restore an example wallet in both applications and measure the result.