First off, there are two different technologies. A Channel Manager ("CM") is something that just keeps all your bookings in check, but does not have the ability to make your own bookings and has more "bare bones" features. A Property Management System ("PMS") has more features, such as messaging, automation and the all important direct booking.
I'm a techie and I did a lot of research as well. I knew from it that I needed to start with a PMS (as opposed to a CM) to prevent double bookings and to help streamline things as our company grows.
I use Lodgify. For the most part I like it, but there are enough quirks where I can't wholeheartedly recommend it at this point (though I have made several feature requests which hopefully will be looked at and make the development roadmap). I looked into several providers (iGMS, YourPorter, Guesty, Snooby, FutureStay and at least two others I can't recall right now).
Several of the providers wouldn't even talk to me with two listings. They have a minimum of 5 or even 10 before they'll even consider setting up a sales call. I ended up going with Lodgify because they were willing to work with a small provider like me and they seemed to have many good features and were recommended on a Netflix show about vacation rentals.
All providers seem to have the basic rates & availability sync, some have APIs with more OTAs instead of iCal syncs. Where Lodgify falls flat is in pre-sale messaging. It does not have the ability to work with inquiries, but to be fair most don't. Some providers do and can automate those messages. That's a huge bonus so you don't have to jump to stop the clock everytime someone inquires about a place or when you get those 2am inquiries and wake up to a 6 hour timer messing up your average response rate.
All providers seem to have a basic website. I'm not a fan of what I've seen so far and am building my own. The ability to accept direct bookings (and not have to rely on the OTAs) is a big ability you'll want.
Accounting is a big deal, especially as you grow. Some offer accounting options, sometimes it's an add-on or only available on a higher priced package. There are some purpose built accounting programs for STRs, so that is something worth considering as well.
We use automated door locks, so integration with a third party to handle that is crucial for us. A nice to have feature would be to notify your staff when a booking is made or ready for cleaning.