The slew of options is in contrast to the smartphone market, where just two operating systems -- Apple's iOS and Google's Android -- dominate.
But more consumer choice will also mean more difficulties for services such as Hulu and Netflix to write apps. As a result, app selection on any given TV will be limited.
To fully enjoy the range of Internet video on the TV, many consumers will still have to buy a separate device such as Apple TV and Roku -- and then figure out how to install it. Those devices cost about $100, though Google sells a $35 Chromecast device with fewer features.
TV manufacturers have been pushing smart TVs to give consumers a reason to upgrade their sets more frequently. The Internet capability also keeps the TV central to households, even as people spend more time watching Internet video.
But so far, apps on smart TVs aren't as extensive as what's found on phones and stand-alone streaming devices, in part because no one operating system has enough users to make it a priority for app makers.
"I keep hoping we will see convergence," said Colin Dixon, chief analyst at nScreen Media, a research firm in Sunnyvale, Calif. "Unfortunately we keep seeing the number of operating systems increasing, not decreasing."
Chet Kanojia, whose Aereo online television service has been trying to expand onto more devices, said the tendency for TV set manufacturers to differentiate their systems with unique features turns app development into "a...