Last year, Piper Jaffray estimated that the four best-selling VR headsets in the world this year would be Samsung's Gear VR, Facebook's (META 1.54%) Oculus Rift, HTC's Vive, and Sony's (SONY 0.37%) PSVR -- in that order. Piper estimated that Samsung would sell 5 million Gear VRs, Facebook would sell 3.6 million Rifts, HTC would sell 2.1 million Vives, and Sony would sell 1.4 million PSVRs.

But now that all of those devices have arrived, newer estimates indicate that Piper's forecasts were likely too bullish. In early October, research firm SuperData estimated that Sony would actually finish the year with the top-selling device, while the Oculus Rift would rank fifth. Let's take a closer look at those shipment numbers.

Sony's PSVR. Image source: Sony.

1. Sony's PSVR

SuperData believes that Sony will sell 2.6 million PlayStation VR headsets this year, although the headset only launched in mid-October. The reasoning is that unlike the Rift and Vive's requirement for newer "VR-ready" PCs, the PSVR works with existing PS4 consoles.

Since Sony has already sold over 45 million PS4s worldwide, it has a huge base of potential users. Moreover, the PSVR's $400 price tag makes it the cheapest high-end VR experience on the market today. Demand for the PSVR has been robust, with the device selling out at multiple retailers, so the 2.6 million estimate (6% of its user base) could actually be very conservative.

PS4 game developers are also adding VR features to their new games, which could convince gamers to buy the headset. It could also boost sales of the PS4 Pro, which adds 4K gaming and better visuals for VR games.

2. Samsung's Galaxy Gear

SuperData expects Samsung to sell 2.3 million Gear VRs this year. The Gear VR only costs about $100, but must be powered by a high-end flagship device like the S6, S7, or Note 5. Unlike the spartan Google Cardboard, the Gear VR adds additional sensors to improve latency for a smoother overall experience. It's also digitally tethered to Facebook's Oculus Home ecosystem of apps and content.

The Gear VR will likely remain a popular choice with consumers who own a flagship Samsung phone but are unwilling to pay hundreds of dollars for a high-end VR headset. The mobility of the Gear VR, which isn't tethered by wires to consoles or PCs, also offers users more freedom of movement.

3. Google Daydream

Piper's older forecasts didn't account for the arrival of Alphabet's (GOOG 0.37%) (GOOGL 0.35%) Google Daydream, a new VR platform which is natively built into Android 7.0. The platform resembles Oculus Home, and is likely intended to be the VR successor of the Google Play Store. Google has also unveiled a headset and remote combo which works with "Daydream ready" phones.

Google's Daydream. Image source: Google.

SuperData believes that Google and its hardware partners will sell about 450,000 Daydream headsets this year. However, that could be a tough goal since the first devices arrived in mid-November and only a few phones (the new Pixel and Moto Z devices) work with the platform. But once more compatible phones are introduced, demand for Daydream headsets, which cost just $80, could rise on similar strengths as the Gear VR.

4. HTC Vive

HTC's Vive, which features full-body motion tracking in VR space, is arguably the most technically advanced VR headset on the market today. However, it's also the priciest at $800, and must be tethered to a high-end PC. The user must also set up motion-tracking boxes around a wide-open "play area" to track the user's movements in virtual space.

That high price tag and cumbersome setup is likely throttling demand for the Vive. SuperData believes that HTC will only sell 420,000 Vives this year, while a Steam survey in September found that only 0.18% of respondents owned one of the high-end headsets.

HTC's Vive. Image source: HTC.

5. Facebook's Oculus Rift

SuperData estimates that Facebook will only sell 355,000 Rifts this year. That's surprising, since Facebook's $2 billion acquisition of Oculus in 2014 arguably sparked the initial land grab in the VR market. However, the aforementioned Steam survey found that just 0.1% of gamers owned a Rift.

Like the Vive, demand for the Rift was throttled by its price tag of $600 and its need to be tethered to a high-end gaming PC. Meanwhile, affluent gamers looking to splurge on a top-tier VR experience were likely drawn to the HTC Vive's full-body experience instead. The Rift's weak debut is troubling for Oculus Home, which could lose ground quickly to Google Daydream as more Daydream-compatible devices arrive in the coming year.

The bottom line

SuperData's numbers paint a much more pessimistic view of the VR market than Piper Jaffray's, but we should remember that these are simply rough estimates. Until these companies report hard shipment figures, we should take these forecasts with a grain of salt. However, we should also note the disparity between cheap mobile/console-based headsets and pricier PC-based ones -- and see if that trend continues over the next few years.