This is such a non-argument. Every non-toy XMPP client supports OMEMO¹, so it makes no practical difference. Signal only supports one single official client and will cut you from your account if you happen to have ergonomics, accessibility or platform preferences that are not supported by Signal. That's the price to pay for Signal's "universal defaults", and that's a tough one if you ask me.
OMEMO is not always-on like Signal, so it doesn't even compare.