If you want to load stuff right off thebbox and not fiddle with drm, your best bet would be an iPad or other tablet.
Personally, I have used both devices and once you have the purchasing and drm removal taken care of, the experience with reading is nearly identical. The kindle is a little faster to use, allows organization of books into collections and has multi-language dictionary support and text to speech. I use those features so they are important to me. But if you don't use them, you can read just as well on the kobo.