Never used changenow.io and I have used the other two for a couple of trades but right now on I'm using binance for my daily trades. And though registrations are disabled, I can jump off to other exchanges like changelly. When I want to step on other exchange this is what I prefer.
about Changelly and verification is a good point.
No ID verification = less hassle.
ChangeNOW is fairly new. Never had a problem with them: no verification, no limits and 0.5% commission