Late last year, Roku came out with an all-new line of products. New branding did away with the old numbered system, and new form factors took over at the lower end of the lineup. But at the top of Roku's line, things look pretty similar: the new Roku Ultra, while slightly smaller, bears a striking resemblance to the old Roku 4. Under the hood, too, things aren't that different when you look at the Roku Ultra vs. Roku 4. And that makes sense considering the Roku 4 was still relatively new at the time of the new lineup's release.Still, there are some differences between the Roku Ultra and Roku 4. The Roku Ultra is a little smaller, and there are even slight differences in hardware. The question is: is the Roku Ultra different enough to be worth upgrading? Here's our complete breakdown of the Roku Ultra vs. Roku 4 question.Roku Ultra vs. Roku 4 The Roku Ultra is extremely similar to the Roku 4, but a few key differences can make or break the upgrade decision for some consumers. Let's take a look at what the devices have in common and then move on to what sets them apart from each other.Roku Ultra vs. Roku 4: the similarities Let's start under the hood. Processing power is very similar between the two devices. Both sport quad-core processors, and there's not a very noticeable difference in speed and performance between the two.Then there's video: the Roku 4 was the first Roku to sport 4K support, and that continues in the new version of the top-of-the-line product. The difference comes in HDR support, as we'll see in a moment.You'll find a lot of similarities on the remote controls. Some lower-end Roku models require you to point the remote at your device when controlling it, as you would with a cable remote. That's not the case with the Roku 4 or the Roku Ultra, both of which have point-anywhere remotes. The remotes also have built-in microphones – both devices support agnostic voice search.The Roku Ultra is the only Roku device that currently ships with those “A” and “B” buttons that the Roku 4 remote also had. Those are the “gaming buttons,” and while they're not essential for streamers and most other users, they are nice to have for Roku's (limited) gaming app selection.Both remotes also have a headphone jack for private listening.The ports you'll find on the sides of the devices are the same, too: you'll have a USB port, a micro SD slot, an optical audio jack, and, of course, an HMDI port.Roku Ultra vs. Roku 4: the differences Okay, now for the important part: what's really different in the Roku Ultra vs. Roku 4?Let's start with HDR video. While both devices support 4K Ultra-HD video, only the new Roku Ultra support HDR video. What is HDR video? This PC Magazine article does a good job of explaining it, but the short explanation is that it is improved contrast range. Some modern TVs have it, so if yours does, you should consider the upgrade to the Ultra. If your TV doesn't have it, though, this does you no good.The Roku Ultra is also a quieter device. The Roku 4 was a near-perfect device, but some of its users weren't fans of its fan. The internal fan that cooled the Roku 4 wasn't deafening, but it was audible. The fan is out on the Roku Ultra, which manages to stay cool without one. No more whirring sounds during your movies and TV shows.One relatively minor difference between devices is hidden in the optical audio input. The Ultra can convert Dolby D+ to the older Dolby D format, which the 4 cannot. This only matters if you're using an older audio receiver.Finally, there's the form factor – which, in this case, comes down a difference in size. The Roku Ultra is a smaller device than its predecessor, which is great news, because the Roku 4 was a little bit on the large size. If space is an issue on your TV stand, take note of this factor!Roku Ultra vs. Roku 4: should you upgrade? That wasn't a laundry list of differences, so the choice to upgrade may be a bit of a close one. The newer device is great, but it isn't cheap, so you don't want to upgrade if you don't have to.To me, the decision is largely based on the HDR video question. If you have an HDR TV, it's time to ditch the 4 and go with the Ultra. If not, you may want to hold off until you get an HDR TV.