On a sunny day in April of last year, Apple released one of most game-changing gadgets ever. (I bought one for myself after waiting in line for two hours.)

The original iPad, a ten-inch touchscreen tablet, rocked not only the computing world but the consumer market in general. One irony is that it also killed off the reigning champ of touch tablets, the 7-inch Samsung Galaxy Tab.

According to a report by Context, monthly sales of touchscreen tablets flip-flopped from a high of 90 percent before the iPad shipped in April and May to only 10 percent of the market after the iPad shipped.

Yet, for some business users, a 7-inch tablet like the BlackBerry PlayBook, the new Cisco Cius, or the Acer Iconia Tab A100 offer a better form factor. And, Amazon recently announced the new Kindle Fire, which will become available in late November for the low price of just $199. (Apparently, the $99 giveaway price for the discontinued HP TouchPad leveled the playing field for tablets.)

John Jackson, an analyst with CCS Insight, says the 7-inch tablet size is obviously more portable and lighter than a 10-inch tab. That makes it more suited for some applications where a lighter tablet makes sense, such as field work and sales. He says, some companies may promote the use of 7-inch tabs for business and encourage employees to use the iPad only at home.

Jackson says some vertical markets may prefer the 7-inch size because it is a good fit for their business – they do not do a lot of document editing, they do not need a movie playing machine, and yet a 4-inch smartphone is just not big enough.

That said, he also mentioned that an iPad is more suited for anyone who creates content. The 10-inch size is also the best for games and watching movies.

“We half-joke that the tablet market is not a market at all, but rather a product that Apple makes that other suppliers have mistaken for a market,” says Jackson. "Such is Apple’s dominance and the absolutely unremarkable performance of all other devices launched to date," according to the actual sales figures.

Still, Jackson says several 7-inch tabs are available and each one offers a unique set of features, and some will appeal to specific business cases. Here are four current models to consider, along with recommendations on where they fit.

1. BlackBerry PlayBook
Research in Motion, the company that makes the BlackBerry PlayBook, recently announced that the PlayBook has sold almost 500,000 units since launch. (Meanwhile, the iPad and iPad have sold well over 10 million units.)

This particular 7-inch tab is the most business-centric model available: it uses a unique app called BlackBerry Bridge that opens a portal to your BlackBerry handheld. Once connected, you can open e-mails as though they were local to the tablet. This means better security: those e-mails all stay on one primary device.

Edge Imaging, a school and sports photography company in Ontario, chose the PlayBook primarily for the business features and security, but they also like the smaller size for portability. The company routinely deals with student photography by e-mails and the Bridge function keeps the photos safe. They were able to deploy the tablets very quickly for sales staff.

“I often notice that the Playbook is carried conveniently wherever our management team or reps go.  They bring it to meetings, restaurants and most importantly to schools,” says Mike Watkinson, the owner of Edge Imaging.

Jackson called out the PlayBook (and the Samsung Galaxy Tab) as unique not necessarily by total sales, but by the amount of advertising RIM and Samsung put behind the marketing effort, and they are generally available in many retail shops.

The PlayBook uses a proprietary OS and runs only PlayBook apps, although RIM has hinted that the device will support Android apps eventually. Like the Acer A100, the PlayBook uses a 1GHz dual-core processor that’s not as fast as the Cisco Cius.

2. Cisco Cius
Another business-minded tablet is the Cisco Cius. Unlike most Android tablets, the Cius is directly targeted at business users. The device supports Cisco EX Series telepresence so you can call up a video meeting in 720p HD video as easily as making a phone call. The 7-inch tablet is also outfitted with Wi-Fi and 4G networking and has a faster 1.6GHz processor than most tablets.

“The Cius may be the most successful product to date as Cisco has stuck to their strict business use case and have not let the media draw comparisons to the iPad,” says Jackson. “It’s a device that  knows what it’s about -- a workplace productivity tool and extension to the PBX --  and doesn’t pretend to be anything else.”

The Cius also has some downsides, however. For one, it does not use the latest Android 3.2 operating system that is designed for tablets and instead runs Android 2.2, the same OS used on the older HTC Flyer and the Samsung Galaxy Tab. That means some apps might look a bit odd on screen, and you can’t run some of the latest Android apps – even those intended for business use.

There also isn’t a good infrastructure in place for media. For those who use a tablet on long plane rides or at home, it means the device is not well-suited for downloading the latest Hollywood movies, TV shows, or music.

3. Acer Iconia Tab A100
The new kid on the block, the Acer Iconia Tab A100 is similar to the HTC Flyer, one of the first touchscreen tablets. The main difference is that the Acer A100 runs the Android 3.2 operating system instead of the older Android 2.2 OS. That means the A100 scales apps intended for the tablet screen size better than older tablets, and even scales older smartphone apps better for the tablet screen.

Like the BlackBerry PlayBook, the Acer A100 uses a 1GHz dual-core processor that runs quite fast even compared to the bigger 10-inch tablets like the iPad 2. For apps, you can choose from thousands of good options including many business apps – many more than you will find on the BlackBerry PlayBook.

The screen on the A100 is more glare-prone than other tablets, however, and  looks a bit muddy (because of the poor contrast ratio) for movies and TV shows.

4. Amazon Kindle Fire
One of the most compelling tablets of the year is also in the 7-inch form factor. The Amazon Kindle Fire is burning with brand new features.

This 14.6-ounce 7-inch tablet uses the same IPS technology as the iPad. Essentially, IPS has a distinct advantage over other touchscreen displays because you can view the screen from almost any angle. That should also help with screen glare problems. (We were not able to test out this tablet since it was just announced.)

Battery life is a standard 8 hours, matching most of the 10-inch models. There’s 8GB of internal storage. The 1024 x 600 is not exactly meant for super-crisp movie-watching, and don’t be fooled by the screen’s 169 pixels per inch spec either. The Samsung 10-inch model has 149 pixels per inch. The Fire will not look as much like a page in a book as the original Kindle models, which used E Ink tech.

The Fire will offer some amazing new features we have not seen before in a tablet. One is a new X-Ray feature for books where you can see summaries of characters or ploy lines, generated automatically. Like the original Kindle models, the Fire will provide a free wireless network called Whispersync that lets you download books. Otherwise, to surf the Web, you’ll need to use Wi-Fi since there is no 3G.

Another really interesting feature: the browser on the Fire will run partly in the cloud. Amazon describes this as a code split: the local device will run the browser as needed, but some page surfing will occur faster thanks to Amazon’s network of computers. The result should be much faster browsing.

Overall, Jackson advises companies to take a long look at all touchscreen tablets. He says to ask questions about the viability of each product: whether it offers extra security options like the PlayBook, whether the apps fit your own business model, whether there are hardware accessories available that match your business, and whether the device fits into your existing IT infrastructure.

And there is one last consideration: even the mighty 10-inch tablet may be getting some competition. Jackson says tablet makers are already considering an even larger size than 10-inches for models that could come out next year. That will make the decision even harder, and make 7-inch tablets seem even smaller.