Honestly? It's all about 90% hype.
Edit: With the caveats that 60hz vs 120hz is a big jump in monitor performance and a higher native resolution can support more resolutions. Then there's contrast ratio. Higher ratios have better blacks and color depth. Last is response time or how fast the pixels themselves can change color. Also, don't buy a European monitor (75/144hz) because they use a different type of electricity for their power grids than the US. Damn you once again Edison.