Tablet buying guide

Typical sizes are 7 and 10 inches, though tablets in sizes in between are also available. In landscape mode, most tablets have the short, wide shape of a digital TV. The iPad's display is squarer, similar to a traditional TV's.

All but a few low-rated tablets offer Wi-Fi connectivity. Most higher-rated tablets also come in a version that can access cellular data networks, including 4G. Monthly broadband access costs $20 and up (most tablets require a 1- or 2-year contract, while iPads allow month-to-month access).

The iPad offers the best detail and most accurate colors we've ever seen on a tablet. It has the highest resolution of any tablet at 2048x1536. Color is excellent. The screen is viewable from almost any angle without image degradation. The display on other tablets can be viewed from almost any direction, too, but some lose contrast at off-angles. Images on certain tablets washed out or darkened when viewed in portrait mode, making for a slightly different view even between left and right eyes. Some displays had a bluish or greenish cast.

A tablet version of Windows 8, called Windows RT, joins the list of major operating systems for tablets, along with Android and iOS. Microsoft itself is among the manufacturers offering a tablet with that operating system. The Surface with Windows RT also comes with Office applications, including Word, Excel, and PowerPoint.

A tablet's capabilities are in large part determined by its operating system. As with computers, being able to upgrade the version installed in the factory makes additional capabilities possible and allows the device to use the newest apps. Apple provides upgrades for the iPad's iOS operating system. The latest Android operating system is version 4, which was designed to work optimally on both tablets and smart phones, and is appearing on new tablets. But many Android models continue to run on Android 3.0, meant for tablet screens. Some of the smaller models still use Android 2.3.

Storage in many tablets can be expanded using USB ports; a few can read USB flash drives. The iPad has no memory-card slot or USB port, but its $29 Camera Connection Kit reportedly has some unadvertised capabilities, such as accommodating a USB keyboard and importing photos from an iPod Touch or iPhone.

Seagate's $200 GoFlex Satellite hard drive lets you wirelessly stream video, movies, photos, and documents to a tablet. It has a dedicated app for the iPad but works with any Wi-Fi-enabled tablet. Apple's iOS5 lets you sync with other iOS5 devices.

One way you can print wirelessly from the iPad is via an AirPrint-enabled Hewlett-Packard printer. Several other printer manufacturers have apps for the iPad and Android tablets that allow Wi-Fi printing.

Acer's Android-based Iconia Tab line is available in 7- and 10-inch sizes.  The 10-inch model is also available in a 4G version with service from AT&T.

The Android-based Kindle Fire HD is a competitively priced 7-inch tablet that provides content to subscribers of Amazon Prime media service, an $80 per year subscription.  Its app store is curated by Amazon.

Apple jump-started the tablet market with its 10-inch iPad.  Now in its fourth generation, the iPad uses Apple iOS, noteable for its intuitive interface and excellent app store.  Apple recently introduced the 7.9-inch version of the iPad, the iPad Mini, which closely mimicks its larger sibling.  The iPad and iPad Mini are also available with 4G service through AT&T, Sprint, and Verizon.

Archos produces Android and Windows RT-based tablets.  Models range in size from 2.8 inches to 10 inches.

Asus produces Android and Windows RT-based tablets.  Its offerings have been limited to 10-inch models.  The EeePad slider has a built-in keyboard.  The Transformer line offers optional foldable docking stations that give the line the appearance and functionality of a netbook.

The competitively priced Android-based Nook HD and Nook HD+ tablets use Barnes & Noble's curated app market.  They are 7 and 9 inches respectively.

Coby produces budget-priced Android-based tablets in a variety of sizes.

Google offers one 7-inch Android-based tablet, the Google Nexus 7.

Lenovo's Android-based IdeaPad line is geared toward consumers.  The ThinkPad line is for business and also uses Android. Both lines have 7- and 10-inch models.

Microsoft offers one product, the 10.6-inch Microsoft Surface with Windows RT.

The Xoom and premium Droid Xyboard lines are Android-based and are available in 8- and 10-inch versions.  4G models with service through Verizon are also available.

Pandigital produces budget-priced Android-based tablets in a variety of sizes.

Pantech produces the Element, an 8-inch water-resistant Android model with 4G service through AT&T.

Samsung's Android-based Galaxy Tab line offers a wide variety of sizes ranging from 7 to 10 inches and includes 4G models with service from all major carriers.  Samsung's newer Galaxy Note 10.1 line has the added features of handwriting recognition and multitasking.

Sony's Xperia Tablet S is a 9.4-inch wedge-shaped tablet, and runs on the Android operating system.

T-Mobile offers one 7-inch Android-based tablet called SpringBoard with 4G service through T-Mobile.

Toshiba's Android-based lines include the 7- and 10-inch Thrive line and the Excite 10 LE, the thinnest 10-inch tablet we've tested.

Velocity Micro produces budget-priced Android-based tablets in a variety of sizes.

The 7-inch Optik model is Android based with 3G service on Sprint.

We find the iPad's squarish screen is better suited to most tablet uses than a rectangular one. Several other tablets have similarly shaped screens, including some from Archos and Lenovo. Rectangular screens held horizontally offer a wider landscape view that's better for watching movies in something closer to a wide-screen 16.9 aspect ratio, and the shape may make them easier to slip into a purse.

Apple provides upgrades for the iPad's iOS, as does Microsoft for Windows tablets. New Android apps may require Android 3.0 or later. Before you buy a tablet with Android 2.3, check if you can upgrade it to 3.0 or better.

App developers create new apps for the Apple App Store first, and more often exclusively, than for the Android marketplace. And because of the large user base, apps in the Apple store are more likely to get bugs fixed first.

The major app stores from Apple, Google, and Microsoft have specific developer requirements that make their apps more reliable and less likely to be vulnerable to malware. But Android devices (only) let you opt to install non-vetted apps from the Internet, so be careful about allowing that.

If you choose a tablet with the Android OS, make sure it has access to Google's "genuine" Google Play market and not just a third-party app market such as GetJar. You'll get a wider variety of popular apps there, and gain some security against potentially malicious "rogue" apps.

You get many fewer Android apps on Barnes & Noble and Kindle tablets because those companies select the apps they want provide. But there's still a large number available on both of those tablets as well.

Microsoft's Windows Store is brand new and so far relatively sparse, but we expect the number of available apps to continue to increase.

Many of its apps outdo Android apps in terms of innovation. Don't forget the iPad's excellent 9.7-inch display for reading magazines and watching movies, as well as its long battery life.

A Wi-Fi-only model is the most economical choice. Tablets with cellular service cost more, plus you'll have to pay for the service. Choose a broadband model only if "everywhere access" to the Net is critical. If it is, 4G capability, or at least the ability to upgrade to it, is a plus.