Check out Autel. They have excellent scanners at various price points. 

I've been using the ThinkOBD 100, bought it after I saw Scotty recommend it on his YouTube channel. Works great for reading and clearing codes. I bought it on Amazon for around $30.

I'm assuming that you're talking about a non-professional scan tool. The most sensible thing to do is to go to the various vendors web sites (such as Blue Driver, OBD Max Plus, Carista, FixD, etc.) and see what functions they offer for the specific vehicles that you want to scan. Do they support each, and at what level? What's omitted? That's the question you'll need to investigate. 

Of course, the same advice holds for more expensive tools, such as Autel, Bosch, etc. As was pointed out in another thread, if you buy any of these from Amazon, make sure that there's warranty and software updates available. (Apparently, that's not the case with an Autel bought at Amazon).

What are you trying to do with the scan tool? You need to figure that out first.  Otherwise, for most people, a basic scan tool is all they need, and for that the Bluedriver is excellent (and works with your smart phone).  It is about $100.  I would buy direct from Bluedriver to make sure you are getting the latest firmware and not getting scammed (e.g. clones, etc).

https://www.bluedriver.com/products/bluedriver-scan-tool

If you need something more advanced (like scanning all the onboard computer modules, more service functions, and/or bidirectional control), then I recommend Autel.  Whichever tool you buy, I recommend you buy direct from the manufacturer (if they offer that option) or from one of their authorized dealers so you can get warranty, software updates, service afterward and to not get scammed (lots of clones out there).

Be sure to also check the manufacturer website to see if your vehicles are supported first before you buy;  if not listed contact them.  They will eventually add them, but it’s still good to check there first.

Click the "Tools" link at the top of the page.