Normally I prefer IPad, but Kindle has 2 advantages – on a light sun it’s much easy to read Kindle screen, and it also have free free wireless internet(but browser is quite limitted),when for my IPad wi-fi is required.
A few months ago I’ve wrote a post about Kindle and ability to transfer articles using Instapaper add-on http://www.wordcycler.com/help.html. I beleive that it’s the most convinient way to pass html files to Kindle.
For iPhone and iPad I love ReadItLater. It saves any articles from web site on iPad Safary.
When you reading inside RIL, you can click on any link and ask to “Read it later” and continue with the main article. Previously In Safary new link was opened in a new tab and it became current, which interrupted reader from the main article.It has been gixed in the latest version of Safary.