Welcome to MR, DazeDreamer
You've come to the right place to get lots of information. If you look at the top of this page on the left side, you can click on the Wiki. Lots of information on devices and formats there.
Some things you should keep in mind when making a decision:
What you would like to read on your device in order of preference and quantity.. NYT best sellers, back titles, sci-fi, classics, tech manuals, library books, etc...
The answer to the above question sometimes determines which reader may have better support.
The various devices support various formats. Not all devices support the same formats. Some may not even support DRM formats at all. When checking format compatibility (as an example) if it lists epub, make sure to find out which it supports ... DRM'd epub or nonDRM'd epub or both ...
DRM locks a book to that particular format and sometimes that particular device. (Sony store DRM format is lrx and can only be read on the Sony. But the Sony does support many other formats so this is not a major problem--- this is my opinion) (Kindle store, Amazon, format can't be read on other devices - I don't have a Kindle so no experience with it)
I'm not bringing up format shifting or DRMing in this discussion as it requires tech savy and may or may not be legal.
Someone will jump in and add to my post and / or correct what I've posted if needed.
Cruise the forums and threads. Ask questions when needed and just have fun.