The PC and Xbox One versions of Forza Horizon 3 both launch today, and it looks like you'll be enjoying a gorgeous (and very good) game no matter which platform your play on. As expected, the PC version can look and run much better, but fully taking advantage of what it offers requires some very high-end hardware.
Digital Foundry has taken a preliminary look at the two versions of the game, offering a comparison in the video below. It highlights some of the key differences in terms of visual fidelity when locking the PC version at 30 FPS. It doesn't, however, show off the HDR support in the Xbox One version, which is something you'll need a HDR display and an Xbox One S to take advantage of (as well as the full game--the recent demo doesn't have HDR support).
It's hard to overlook just how incredibly good the game looks when running at 4K and 60 FPS on PC. Another video shows off what this looks like, though you'll need a 4K display to get the full experience.
Perhaps more interesting is the type of hardware you need to run the game at 60 FPS. Digital Foundry played at 4K/60 FPS using an overclocked Core i7 and a Titan X Pascal, which is an expensive setup, though most people likely weren't expecting to achieve those settings with anything less. What's odd is it found that achieving a steady 60 FPS at even 1080p was a challenge with lesser hardware.
"Typically, a game that runs flawlessly at 4K on the new Titan X should run perfectly with performance to spare on Nvidia's GTX 1060--but not Forza Horizon 3, which actually runs significantly more slowly," Digital Foundry's Richard Leadbetter wrote. "The GTX 970--quite possibly the most popular enthusiast-level GPU installed in the most PCs today--shows a huge performance deficit compared to the 1060, but its shortfalls are nowhere near as pronounced as the R9 390 compared to the new RX 480, with a gap often in excess of 20 FPS(!). Bearing in mind that the R9 390 outperforms the RX 480 in many titles, this differential is remarkable."
More curious is the fact that even a Titan X Pascal encountered issues running the game on Ultra at 1080p with 4x MSAA. MSAA appears to be the source of many of the problems, and you should disable it if you encounter performance issues. However, this doesn't solve everything.
Locking the game at 30 FPS, which is obviously not ideal, also makes it possible to run the game smoothly with MSAA enabled even on an i5/GTX 970 setup. Unfortunately, pop-in appears to be an issue across both versions of the game, regardless of hardware configuration.
It's possible some of these PC performance issues will be ironed out with patches and new drivers. For now they're something to be aware of for prospective players without super-high-end hardware, particularly with the PC demo still not available.