MaximumPC uses Coverleaf and PC Magazine uses Zinio. Zinio appears to have the larger library, but Coverleaf does have recognizable magazine names. One big difference is that Zinio allows you to use an optional desktop client whose use is obviously directed at offline reading. That’s a nice feature. The desktop client also has annotation features missing from the bare-bones web client. However, the web client has a feature sorely missing from the desktop and that is the ability to save and share links to pages. You can even send the link to one of the various social networks like Delicious. I use Delicious to save links to articles that I might want to refer to in the future.
The reading experience is much better on my slate tabletPC using the Zinio desktop client. I can move from page to page by clicking corners of the pages. I’ve rigged up a similar thing on Coverleaf by using a mouse gesture extension that emulates pageup/down keystrokes. Note that this only works in Internet Explorer. Firefox for some reason does not move you from page to page with keystrokes.
If it matters to you, Zinio is a Flash-based web app and Coverleaf is Ajax. Both are pretty good, but clearly Zinio “feels” a little smoother. That said, Coverleaf actually has a couple features that Zinio doesn’t. In particular, I like the Pages function which displays a page of thumbnails of all the pages in the issue.
Now obviously you don’t really need to pick one over the other. You can use them both. At least the hardware you need is the same…ie a PC and a web browser. It’s not like trying to decided between a Kindle and Sony Reader.
I suppose that while I’m at it, I should mention my other favorite electronic subscription service and that’s NewsStand.com. Here you’ll find lots of newspapers, like LA Times, NY Times and USA Today.