I'm highly biased towards larger screens, so I'd say go with the 83 inch. I have an 85 Samsung Q80 and I like the size. This is somewhat subjective, of course.
In my non-expert opinion, a smaller TV might be better for gaming because your eyes can take in a larger portion of the screen (at a given distance). I find the 85 less than optimum for gaming because I miss things happening on one side of the screen when I look at something on the other side of the screen. I like the immersive experience, but I tend to get knocked off on multiplayer games because I get focused on one part of the screen (I'm not good at these games to begin with; a better player might not have this problem)
I recently replaced a 75" Q6 with a 77" C4 and I don't notice the size difference.
In the B4 line there are some differences between the 83" and the other sizes:
>>>We tested the 65-inch LG B4 (OLED65B4PUA), and the results are also valid for the 48, 55, and 77-inch models. . . .
The 83-inch model shares a lot of similarities with the
LG C4 OLED. It uses LG's Alpha 9 AI Processor Gen7, supports a 144Hz refresh rate, has three USB ports, and a 2.2 channel speaker system, all of which are the same as the C4. Due to these shared features, we expect the 83-inch model to perform more in line with the C4. However, it doesn't have LG's Brightness Booster technology like the C4 does, so it isn't as bright overall.<<<
The LG B4 OLED is LG's entry-level TV in their 2024 OLED lineup. It sits below the LG C4 OLED and uses LG's α8 AI Processor 4K, which is designed to provide bett...
www.rtings.com
I'm not sure how much difference there is, but I'd want to see an 83 before buying one.
Rtings says the 83" C4 is the same as the other sizes, except the 42 and 48:
>>>We bought and tested the 65-inch LG C4 (OLED65C4); these results are also valid for the 55, 77, and 83-inch sizes."
The LG C4 OLED is the 2024 iteration in LG's popular C Series lineup and replaces last year's LG C3 OLED. It sits above the LG B4 OLED and below the LG G4 OLED. ...
www.rtings.com
If you go with a Samsung S90D, the 42, 48, and 83 are WOLED, whereas 55, 65, and 77 are QD-OLED.
The Samsung S90D/S90DD (QD-OLED) is a high-end TV in Samsung's OLED lineup and only sits below the flagship Samsung S95D OLED. The TV features Samsung's new Neo ...
www.rtings.com
Personally, I find the variations within certain model lines annoying, especially in the Samsung line. It appears to me that they want to market the S90 as QD-OLED, but 83 inch QD-OLED panels are not yet available so they slipped an 83 inch WOLED into the lineup using the same model line designation.
I'm not sure if these variations within model lines make much difference, but it's something to check out before making a final decision.