I like them both but would choose Kindle for PC if I had to pick one.
Now, these books just seem to appear on my Kindle, and on my Kindle for PC. So I find one I want to buy the digital version of and I click Through to get the digital book, which I assume is DRMed. They used to be really cheap for most books, but nowadays they costs more. I'm browsing books on Amazon and there is an option to buy the Kindle ereader version of the book.