Well 24 inch just means that the screen is smaller so its easier for you to see more at once without having to move your eyes as much. But like I said the difference really isn't that big unless you go hard on competitive FPS and hit high ranks. 24inch monitors also often 1080p and those are easier on your PC and you get more FPS.
Also its about the price. 24inch 360hz monitor will cost less than 27inch 360hz monitor: size, resolution, panel type, amount of hz all contribute to the cost so for example often esport focused monitors with very high refresh rates are 24inch in 1080p with cheaper panels, because the target audience of those usually don't care for visuals or color accuracy and just focus on competitive edge. And that is how they can still be reasonable priced. While for example 4K monitor with 360hz would be very expensive.
So overall I'm saying is that as long as the monitor has decent refresh rate (like 165hz or above) and low latency it shouldn't matter too much for most. And that is why I would rather focus on visuals and colors instead of maximizing for competitive play. It gives more flexibility. I used shitty 24inch, 1080p, TN panel, 144hz(at the time it was high) Zowie monitor for years because I wanted to give myself maximum advantage while in reality I was just average casual gamer. But now I finally got 27inch, 1440p, IPS monitor with 240Hz and pretty much all gaming feels much better because the resolution and colors make games multiplayer- and singleplayer, videos etc look so much better. All Im saying is that value visuals instead of maximum performance unless you think you can make it pro or only enjoy gaming for competitiveness.