Modern smartphones often come in two or three different variants, with the chief difference between them being the amount of storage contained within the device. The most obvious example is the Apple iPhone, which is sold in 16 GB, 32 GB, and 64 GB models. The upgrades aren't free, of course, and it often costs $50 or $100 to jump from one storage option to the next.

This raises the question: Which option is best for you, and how do you choose? There are a number of criteria to help make this decision easier, and InformationWeek offers a few tips to help out.

Expandable or Not?

These days, there are two types of devices: those that have expandable storage and those that do not. Just like smartphones that have removable batteries, smartphones that have expandable storage offer more flexibility than those that are locked down.

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Good examples of locked-down devices include the Apple iPhone, HTC One, Nokia Lumia 920 and Google Nexus 4. These devices have finite amounts of storage. There are many others, but these are perhaps the most visible today. Some examples of devices that offer expandable storage include the BlackBerry Z10, Samsung Galaxy S 4 and Motorola Droid RAZR MAXX HD.

Expandable storage is offered in the form of a microSD memory card. These little cards are available in sizes between 1 GB and 64 GB, with the most common options 8-, 16-, 32- and 64-GB. Prices vary by storage and speed (how fast the card reads/writes data). For example, an 8-GB Class 4 card (slower speed) from SanDisk costs just $7 when purchased from Amazon.com, and a 64-GB Class 10 card (very fast) from Kingston costs $55 from Amazon.com. Expandable storage offers the best bang for the buck.

If Your Phone Has Finite Storage

Suppose, for whatever reason, you need to go with a device that doesn't offer expandable storage. No big deal. Most sealed smartphones stick with the 16-, 32-, and 64-GB options. Which is the best for you? That depends on how you use your phone.

Do you download lots of apps but rarely listen to music or video? If so, it's probably safe to stick with one of the less expensive options. Phones with 16 GB of storage offer plenty of space for apps (even big games) and photos and still leave plenty of room for hundreds of MP3s and even a full-length HD movie. If your smartphone serves more as an information source than an on-the-go media server, save yourself some green.

Do you hoard media? Have an epic media library on your PC at home? If having instant access to thousands of songs and dozens of movies is important to you, then it makes sense to choose the option with the largest amount of storage. Keep in mind, however, that going from 16 to 64 GB often makes a $199 smartphone a more painful $399 at the register.

If Your Phone Has Infinite Storage

Okay, no phone actually has infinite storage, but you know what I mean. Devices that accept microSD memory cards present many more options. For starters, microSD cards can be swapped out at any time. You can fill up one card with music, another with movies, and leave a third blank for taking pictures and video.

Here's a real-world example: Samsung plans to sell the Galaxy S 4 in 16-, 32-, and 64-GB options, same as the iPhone. However, the S 4 also accepts microSD cards. The difference between the 16-GB model and the 64-GB model will probably be about $200 at the register. You can choose the 16-GB model, though, and pair it with a 64-GB card (totaling 80 GB of storage) for only about $50 more. Need more than 80 GB? Buy another card to supplement what you already have.

If you want as much storage in your smartphone as you have in your laptop, pick the 64-GB model and pair it with a 64-GB microSD card. Having 128 GB in your pocket is kind of crazy, but it's certainly an option.

What About the Cloud?

Cloud services throw a bit of a curveball into the entire equation, but they don't present an unsolvable problem. A number of services have sprung up in recent years offering online storage that can be accessed directly from smartphones. Some examples include Box, Dropbox, Google Drive, Microsoft SkyDrive, Apple iCloud and so on. Each offers some storage (2 GB - 5 GB) for free, with paid options that range up to 1 TB if you don't might coughing up a small fortune.

The best use for these services, I've found, is as a backup option. Want to make sure your vacation photos aren't lost when your phone falls into the drink? Set it so that all your images are automatically uploaded and synced to one of these online accounts. Cloud services also make it easy to share photos -- ahem, and work files -- that you may need to upload from a smartphone. Of course, you can choose to use cloud storage however you wish, and adding them as a virtual security deposit box to the storage on your device offers some piece of mind.

Want to store your music and/or movies online instead of on your phone? Go with something like Google Play Music, Amazon MP3 or Apple's iTunes Match. Each of these will accept up to 20,000 songs (for an annual fee of $20 - $25), which can then be streamed over Wi-Fi, 4G or 3G to your smartphone without taking up any local storage space. Using cloud services for music playback is particularly appealing if you have a device that's limited to 16 GB of storage but you still want access to lots of tunes. The downside, of course, is that your music will not be available for playback offline (for example, on a plane) unless you choose to sync at least some of it to the local storage.

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