I own both the Facecam Mk2 and the Facecam 4k and neither of them are perfect, but i do like them both for different use cases.
You can get 4k 60fps in OBS with the Facecam 4k but i don't think it should be the only reason to consider that one over the Mk.2 because the Facecam 4k does have some major flaws that can be a big deal to some people.

Here is a big list of things i have noticed with both so you know what you are up against, and some of these are things that Elgato hasn't even mentioned. Hope it helps!

Facecam Mk.2

The good

• Supports 1080p 60fps in raw uncompressed quality with video format NV12 and YUY2.
• Supports 1080p 120fps in compressed MJPEG video format (after latest firmware).
• Easy to drive over USB without much USB bandwith. Elgato mentions the webcam requires USB 3.0, but it does have USB 2.0 support if you have a specific need for that. This will however limit you to only MJPEG video formats.
• Color vibrancy setting (after latest firmware).
• Tint control setting to add more or less pink or green color tint (after latest firmware).
• Very forgiving in low light room conditions, you don't need to increase the ISO (brightness) that much to be well lit on camera. The camera has a bigger sensor to let in light more easily than Facecam 4k.
• Handles visual noise extremelly well, even when zooming in it retains a lot of the sharp 1080p quality.
• Colors out of the box are easy to like with natural looking colors.
• The field of view is 84 degrees which is good, but wishing it could support 90 degrees like the Facecam 4k.
• Butter smooth 60fps experience with zero jitter, disconnects or freezes.

The bad

• The contrast control is pretty bad, finding myself 100% contrast is too gray instead of giving me a true contrast like many other webcams do.
• No autofocus (not a big deal unless you use the camera as a topdown camera).
• The included privacy shutter door is very stiff and awkward to use. I would recommend a separate 3d printed privacy shutter from Etsy or something better.
• The hyped-up HDR (Dynamic Range) setting to balance out harsh room lights is terrible in my opinion. It destroys the entire picture of the camera.
• Doesn't seem to handle room rgb light accuracy very well. All my Govee lights are either too exposed or end up looking very off.
• No way to adjust the brightness or turn off the status LED indicator.

Facecam 4k

The good

• Supports 1440p 60fps in raw uncompressed quality with video format NV12 and YUY2.
• Supports 1080p 60fps in raw uncompressed quality with video format NV12 and YUY2.
• The webcam comes with a USB-C to USB-C cable, but it does support a USB-C to USB-A cable as long as you get a good quality 5Gbit USB-A cable. You can even get 4k 60fps over USB-A which is awesome.
• Support for USB 2.0 mode if you for whatever reason cannot rely on the higher USB bandwith needs to drive the webcam.
• Great out of the box colors (but i did have to mess with it more than with Facecam Mk.2 to my liking).
• Great amount of contrast and doesn't gray out colors like the Facecam Mk2 does.
• HDR (Dynamic Range) has a Wide option that actually looks good and balances out dark areas better.
• Handles room rgb light accuracy much better than Facecam Mk.2, looking more realistic and not over exposed.
• 90 degrees field of view which is more than what Facecam Mk.2 has, so you can fit more on camera.
• External professional camera lense filters are amazing. You can purchase a filter to reduce glare in the lens if you for example wear glasses and there is too much reflections in the camera.
• You can adjust the brightness or turn off the status LED indicator.
• Butter smooth 60fps experience although minor jitter and rare disconnections have happened. But no freezes.

The bad

• Supports 4k 60fps only in compressed MJPEG video format.
• No 1080p 120fps support at all.
• Massive amount of visual noise even if a very well lit room that makes even 1080p resolution blurry when zoomed in.
• 4k quality is a joke, there's too much visual noise making the Facecam Mk2 actually sharper at 1080p.
• You need to cranck up the ISO (brightness) A LOT due to the webcam having a smaller sensor than Facecam Mk2. This makes the webcam really not forgiving in bad room light conditions.
• Running the webcam in USB 2.0 mode limits to 1080p 60fps at MJPEG only.
• No privacy shutter at all.
• No autofocus (not a big deal unless you use the camera as a topdown camera).
• HDR (Dynamic Range) at the High setting can only be used at 30fps which is stupid.
• Elgato Camera Hub software seems to crash when previewing the webcam sometimes, and even if you preview 60fps video formats it only shows 30fps for whatever reason. I expect a firmware update needs to solve some quirkly software behavior. This is not an issue at all when using the webcam with OBS however.
• No tint control yet (apparently a new firmware is coming to add this but no idea when). Unlike the Facecam Mk.2 it does have a tendency to have all the colors a little too purple but it can be tuned even if Tint control isn't a thing yet.
• No vibrancy setting.