Yeah it's definitely worth spending 500~ bucks on a monitor with medium image quality and worse responsiveness, that will have literally no benefits to any game but osu, (not really though, given you might get more lag) unless you have the setup to also run other (more demanding) games ABOVE 144hz.
Not mentioning that in several games a refresh rate of 240hz isn't really beneficial (league).
Obviously Momiji will come along and say that it makes a calculated 0,000123% difference that, on a scale of a 100000 playcount COULD potentially net you one or two misses less, not factoring in that it might screw with the way you've adjusted to your reading which probably also give you a few more 100s here and there, maybe a miss (I know I had a similar experience on 60hz vs 144hz when it came to bhopping)
However, Momiji is not factoring in the increased response / input lag that certain monitors bring with them. The ASUS VG248QE has the lowest input lag on the market right now IIRC, while the newer 240hz models have a slightly higher delay to them, so you actually would be downgrading in terms of osu! if we were looking at it realistically.
The AOC AG251FG has twice the input lag of the VG248QE, the ViewSonic apparently comes with an input lag four times higher than the ASUS VG248QE.
You can't really judge a book by its cover. Just because a panel comes with 1ms response and a higher hz doesn't necessarily mean it has 1ms input lag / response time in a realistic environment.
Now I'm not saying 240hz isn't desirable, but it's reaaaally not worth the investment JUST for the improved frame rate which really only affects one game at best. If you play something like L4D2 or anything "twitchy" and where you can get a stable 240FPS or atleast over 144hz granted you can make use of G-sync or variable sync, then it also benefits you there.
For osu however I feel it's more giving a smooth feel to the entire game rather than actually noticably boosting your performance, and in case of input lag & responsiveness, you'd actually be downgrading if you changed from a VG248QE to a 240hz model right now.
There are obviously other benefits like no PWM and sometimes better image quality, but given the right preset you can have a decent image quality on the VG ( and other TNs ) already.
TL;DR
Don't go 240hz. Wait until it's cheaper or IPS 144hz panels get cheaper so you can have both smooth gameplay and good image quality.
Frikandel wrote:
placebo is a word used to describe when no change is perceived and turned into an improvement
going from 3.4722222ms average latency to 2.083333ms average latency, and stuff like that, is not placebo because there is an existent change
Hence it would be placebo. You don't perceive a 1,4ms change in latency.