Remember this as you shop for the must-have gadgets of the season: You're buying far more than a box of circuit boards when you pick up a smartphone or tablet. You're picking a set path through the digital world — and turning back could be painful.



As the tablet and smartphone markets grow more competitive, companies are stepping up the range of content they offer exclusively to customers as a way to stand out in the marketplace. Apple offers a bevy of quality apps and music through its iTunes Store. Amazon touts access to its enormous online marketplace. Google offers seamless integration with its mail and documents system. But what people often don't realize is that each 99-cent app or $2 song sinks them deeper into a lasting relationship with the company that sells stuff to run on their gadgets.



"I don't think it's something that everyone considers, but it's something that they should," said Carl Howe, an analyst with Yankee Group. "Particularly with mobile devices, there can be as much investment in the content in the device as with the device itself."



In other words, over the course of a year or two people can spend hundreds of dollars on songs, movies, apps and books that they often can't transfer to another brand of smartphone or tablet.



If you pick an iPhone this Christmas, do it with the knowledge that a lot could get stuck there if you switch to a different smartphone down the line. Even apps made by the same companies won't transfer between devices. Buying Angry Birds on your Kindle Fire will never make it show up on your iPhone — you'll have to buy it twice.



This lock-in is becoming even more pronounced as companies introduce families of devices that share app stores and information. Apple, Google and Microsoft all point to this cloud storage capability as a major selling point as they hawk their lines of smartphones, tablets and, at least for Apple and Microsoft, computers.



On one hand, that's great for consumers, who may want to be able to note something on their smartphone during a commute and have it show up later on their desktop at home. But it also creates a much stronger "halo effect" — the term technology analysts use for the buyer habit of sticking with a single company's gizmos because it's convenient.



Shoppers with iPhones looking for tablets naturally gravitate toward the iPad, for example, because they know their movie, music and book collections will appear on both devices instantly. According to a Yankee Group survey of 12,000 consumers, 78 percent of iPhone owners also have iPads, while only 21 percent have Android tablets.



A smaller survey conducted by Yankee Group showed that current device ownership is a strong predictor of future buying habits. For example, 91 percent of iPhone owners would buy another iPhone — and that's a shorthand explanation of why tech industry insiders and investors are so obsessed with who is up and down in market share.



Worldwide, Apple has the advantage with more than 50 percent of the tablet market, while Google holds around 75 percent of the world smartphone market, according to figures from the International Data Corp. But the landscape is ripe for change as more people snap up tablets in the coming year. The United States, in many ways, is the nexus of the growing tablet market, and in July, comScore reported that Google held just more than 50 percent of the market to Apple's 30 percent.



There are a couple of ways to avoid lock-in, particularly when it comes to things you create yourself. Companies are starting to release apps into each others' stores to make lock-in a bit less drastic. For example, you can get your Kindle books on your iPad or your SkyDrive documents on Android tablets with a limited amount of fuss. But those apps don't come with all the perks of going all-in with a certain company. Kindle apps, for example, don't get access to Amazon's lending library of free books — even for users paying for the company's subscription service.



All this boils down to this: To avoid being stuck with a platform down the road, it's best to think carefully about a device before buying. But before you rush off to create a spreadsheet comparing processor speeds and screen resolution, take a moment to think about how you'll actually use a device. Do you want something for light email, or to replace your laptop? Do you want a phone with a big screen or one with strong apps? Make those decisions first, and let them guide your purchases.



"So many people get wrapped up in trying to optimize a purchase," Howe said. "My best piece of advice is to try things out and buy things you like. "