My verdict: the appointment booking standard, but has become too expensive.
Calendly is ultra-simple: you share your link, people choose a slot, and it's in your calendar. Integration with all calendars (Google, Outlook, iCloud) is smooth.
The network effect plays: everyone knows Calendly, so it's reassuring for your prospects.
What I like less: pricing has become excessive. The free plan is too limited, and paid plans have increased regularly. Cal.com offers more for less.
My advice: if you want absolute simplicity and budget isn't an issue, Calendly remains a classic. But look at Cal.com before committing - you could save significantly with more flexibility.