In my opinion, a 24" monitor is too small for 1440p. That's the 1080p sweet spot (27"-30" being the sweet spot for 1440p). With that said, it's a highly subjective question based on personal preference and what your eyes can appreciate as well as the games you play.
For my eyes and games, I prefer 1440p at 60Hz over a faster 1080p monitor (and I've used both). Most of my gaming is racing (Project Cars, DiRT Rally/DiRT 4, Assetto Corsa, RaceRoom Experience) and there is no noticeable difference between 60Hz at 1440p and 120Hz at 1080p (both Vsync FPS capped).
I much prefer the higher resolution as it helps with track draw distance and clarity on what's ahead. Now for shooters, specifically FPS shooters, there's a noticeable difference. Especially when moving the mouse view around rapidly. It's much more fluid. Others may have a completely opposite opinion, but that's mine as one who has used both types of monitors.