The Kindle Fire HD has the least satisfactory browser experience. Its Silk browser is noticeably slower to load -- sometimes excruciatingly so -- than the other media tablets. And it often reports itself to websites as a smartphone, causing you to get the mobile versions of websites rather than the desktop versions. Plus, Silk responds jerkily to zoom and swipe gestures. Silk is anything but smooth. The Amazon Appstore has no other browsers available for it, so you're stuck with Silk.
Silk offers good bookmarking and history capabilities, but no private-browsing modes, no cross-device tab syncing, no on-page search capabilities, and no built-in sharing capabilities, as both the iPad Mini and Nexus 7 do. Silk has good HTML5 compatibility, scoring 358 points, and its AJAX support is better than Android's or Windows RT's, and nearly equal to iOS's. Too bad using the browser is so frustrating.
Messaging. If you're under a certain age, you text more than you email -- but standard SMS messaging is not supported on tablets. On an iPad Mini or any iPad, you can use Apple's iMessage service to message other iOS and OS X users.
If you don't want to restrict yourself to just people using Apple hardware, you can install a variety of messaging apps such as AOL Instant Messenger (AIM), Google Talk, and Yahoo Messenger, or you can message across multiple services using an app like IM+ Pro. The same options are available for Android devices such as the Nexus 7. But of these, only AIM and a version of IM+ Pro called IM+ All in One are available for the Kindle Fire HD.
Apple's FaceTime is an easy-to-use video-calling service, but it too is restricted to iOS and OS X devices. For cross-platform video chats, you'll want to use Skype, which both the iPad Mini and Nexus 7 support. But not the Kindle Fire HD. In fact, I couldn't find any video chat apps for that media tablet.
Wi-Fi support. In addition to 2.4GHz Wi-Fi networks, the iPad Mini (like the third- and fourth-generation iPads) supports 5GHz Wi-Fi networks, which usually provide faster connections and greater signal reach, letting you access the Internet in more places and faster. The Kindle Fire HD also supports both 2.4GHz and 5GHz Wi-Fi, though its Silk browser was still noticeably slower than the iPad Mini's and Nexus 7's. The Nexus 7 supports only 2.4GHz networks.
The Web and Internet winner. The iPad Mini and the Nexus 7 outshine the Kindle Fire HD when it comes to their online capabilities, tying in this category as the best.