The following is my opinion only, and not meant as a slight against the iPhone and iPod. First, I have to read technical documents as part of my profession. These are predominantly in pdf format. Now, both the Apple iPhone and iPod have fairly functional pdf readers. Namely, the one built into the Safari browser. This is also true of the Motorola Droid. However, the Droid offers an SD card, and an easy path to side load a pdf file from your computer (Windows, at least). Of course, you need to mount the file system from the phone, so that windows can see it. Anyway, once you see it in Explorer, you can drag and drop to your hearts content. Eject the Droid by right clicking the USB "Safely Remove Hardware" icon on your taskbar, and finger drag the menu bar on the top of the Droid screen to dismount the Droid file system. Use a free Droid app like ES Explorer to browse the sdcard, and double tap the file of interest. The zooming is natural (intuitive) on the Droid, and with the device in landscape mode, you can browse the document with the scrolling pad. No touchscreen manipulations are necessary to go from page to page.
Have I ever loaded big books into the Droid? Yes, a 40+ MB art book!
Now, you might be interested in what the Droid can do with non-DRM epub books. The small amount of experimentation I have done has involved the free Aldiko reader. It's not the greatest thing since edible pages, but at least it is free and undergoing improvement:
http://www.aldiko.com/support.html#faq987438943
Chapter navigation is flaky, but text rendering is excellent. I have a massive book edited by Otto Penzler that gives the Sony and Amazon readers a fit.
Aldiko offers a menu page to download ebooks from internet sources. I have not tried this yet.
And that, in a nutshell, is my summary of the Droid's document capability vs. the iPhone/iPod.