Roku just released three new 4K, ultra-HD streaming devices, starting at only $40 - here's how they stack up against Google's and Amazon's

The Premiere+ is a Walmart exclusive. It's identical to it cheaper cousin, with the notable exception that the remote has a microphone so you can search Roku content with your voice.

The Roku Ultra isn't receiving any significant upgrades from its previous iterations. But it will now include a pair of JBL headphones for free, usually priced at $40.

Those headphones will come in handy, too: One of the main differences between this model and the cheaper devices is that users can plug headphones into the Ultra's remote. That allows them to quietly listen to streamed shows or movies without bothering or waking anyone else in their home.

here's also a "lost remote finder" feature, which plays a sound from the remote after you press a button on the Ultra device. Like the Premiere+, the Ultra features voice control via remote.

Aside from a nicer remote, the Roku Ultra also supports 1080p and 4K streaming, additional storage through micro SD cards or USB, and a "night listening" mode that levels out the sound by lowering high-volume moments and raising low-volume moments. You can also connect the Ultra to the internet via an ethernet port, if the wifi in your home isn't optimal for streaming — a feature that the Premiere lineup lacks.

All three Roku devices are advertised as having access to more than 500,000 movies and TV shows.

Google's 4K Chromecast Ultra is pretty similar to what Roku offers, but at $70, comes at a higher price than Roku's entry-level options.

However, the Chromecast Ultra features an ethernet port, something that Roku's Premiere lineup doesn't have. It's also compatible with the Google Assistant and Google Home devices, so you can control it with just your voice, no remote required — but Roku just announced compatibility with Google Home and Assistant as well, so that gap is narrowing.

It should be noted that the Chromecast is purely a streaming device, and doesn't feature internal storage like Amazon's or Roku's devices.

Amazon's 4K Fire TV is also pretty similar to Roku's lineup. It's not clear whether the price drop from $70 to $40 is a temporary reduction, or a permanent price drop.

The Fire TV has an ethernet port, 8GB of internal storage, and supports voice control via Alexa through the remote. It's also compatible with Amazon's Echo lineup of home speakers, so if you're already invested in the Amazon ecosystem, the Fire TV might make the most sense. Roku's devices currently do not support Alexa control.