I have to confirm that the Studio Display is a much better monitor than the LG Ultrafine.
My work let me take home an LG Ultrafine 5K that wasn't being used for this weekend. I've had it plugged into my 2021 Macbook Pro 14 and what I can't get over is how much worse the color quality is when compared to the built-in display on my 2015 iMac 5K. It has a slight green tint to it which drives me crazy. There's subtle color banding in greyscale gradients which is not present on the iMac.
No matter how I try to adjust the white point and color on the LG, it just doesn't look as good. Eventually I got frustrated and went back to using my 2015 iMac.
Meanwhile I've used the Studio Display (I don't own one yet, order is in progress and won't be here for a bit) and the quality is at least as good as the panel in my 2015 iMac, probably better. For me the quality difference is an absolute no-brainer and it's definitely worth the extra money to go with the Studio Display.
I'd have to wonder if it's just the screen you have. For years I used a 27" 2015 retina iMac, and then added in a (used) first-generation 27" LG 5K Ultrafine. I used both displays side by side for photo editing and I never noticed a difference. Never calibrated either of them, so I'm sure if I really tried to scrutinize it then I might find something, but nothing ever stood out at me.
The only downsides I found with the displays were shared by both, as they use the same panel. One was ghosting: leaving something light an item on screen for a few minutes and then shifting to something dark would result in a "ghost" image in the dark space - menu bars, desktop icons, and window buttons were frequent offenders, although the "ghost" image would fade away within a minute or two. The other developed over time, and is best described as pink fringing bordering the screen. People have suggested that there was some sort of adhesive that Apple used that discolored as it aged. It was worst on my iMac; it's present but not as prominent on the LG Ultrafine, but I'm not sure what the age difference is, and expect it to get worse.
It remains to be seen if the Apple Studio display will develop any of these issues. As of now I can say that it does not have the ghosting issue (which I believe was resolved even in the 2017 iMacs; the 2015 models represented the first time you could buy a 5K 27" display), and there's no discoloration at the edges. Image quality seems the same, to my eye - which isn't a bad thing. The monitor physically looks nicer, and the speakers are really impressive - they only fall short of my dedicated Logitech speakers in the bass range, which is expected, since they can't compete with a dedicated subwoofer. One disappointment is the adjustable height monitor - because of the way that it's an arm, the distance between you and the screen changes as you adjust the height. The Ultrafine may not look quite as nice as the Studio Display, but its height adjustment is along a simple pole that is pretty easy to adjust. I'd guess most people will choose to save money and won't get the height-adjustable version of the display, or they'll be using it as a solo monitor. But if you're picky about getting your monitors tightly aligned, trying to align two Studio Displays that aren't exactly side by side (my monitors "wrap around" my desk slightly and thus their footprints are offset) would probably be frustrating, because then you have to worry about matching both heights and depth.
Overall, I'm pleased enough. I do think it's a slightly poor value for the money, though, unless you'll use every feature to the max (speakers and webcam). I knew what I was getting when I paid for it, but I'm still disappointed that Apple didn't try to push the envelope to make it a microLED or OLED display, or to include more ports to make it more like a Thunderbolt hub. Looking at the ports and overall display, itself, it's really no different than the LG Ultrafine, but it costs more - significantly more, if you want to try and match height adjustment.
