Form Factor?

I read RSS feeds...lots of them. It's how I get most of my news. But I've noticed lately that I use different apps on different platforms to read the same feeds. The Sage extension for Firefox on my iMac and MacBook, Pulse on my iPad, and Reeder on my iPhone. The differences seem to come down to which app renders content best on the screen size available. Wait, isn't that at the heart of something called "form factor"? Hmmm, maybe there's something to that idea after all. What do you think?