I've had both IPS and 120Hz and yes the difference is night and day, night and day in favour of the IPS and it's superior viewing angles, uniformity and better colours!! Most people I know, in fact no scrap that, ALL the people I know would much rather have a v-synced steady 60fps with all the eye candy turned up to the max on a decent IPS panel, rather than play on some washed out 120Hz TN monitor with all the LOD turned down just because you're on a quest for maximum framerates and some super twitch gaming!
If you put any "average Joe" in front of my previous 120Hz monitor (Acer GD235HZ) and my current 27 inch Dell then I can guarantee you not one of them would go for the Acer, unless of course "average Joe" was indeed blind
Would have to agree with clippa that the fact you have ysync on says it all. Iv had the Asus vg236h and currentlly using a 3007wfp-hc and playing with vsync enabled on 60hz screens on fps games just fills so wrong. Mouse movments doesnt fill as responsive and turning around seems slower. Id rather play with it off while geting 100fps even if theres more tearing which doesnt really bother me. But a 120hz monitor would mean no tearing up to 120fps with vsync off and you being able to spot stuff more while moving around a lot. So anyone currently playing on 60hz screen with vsync off would benefit from a 120hz screen
Im concidering geting the LG for fps games because i move around a lot while killing enermys and because i find smaller monitors better for close combat fights
I only brought this dell because it was 30inch 2560 x 1600 which i got for under £500 and has very low input lag. But if it came down to 24 inch ips vs a 23-24 inch 120hz monitor then it would be 120hz all the way because performance wins over image quality if your playing to win
But id always prefer my dell for single player games or non serious online gaming