Yes, there is no way a H50 will perform to the level of a 'proper' water-cooling kit. I for example have an EK-Supreme and PA120.3 which keeps my 920 nice and cool @4.2GHz (30'C Idle -50'C Load). My temps suggest that I could push further; however, the limiting factor quickly becomes the heat generated by the mobo at these increased voltages.
I could easily watercool the mobo too, if I had the money, which would allow for an 'extreme overclock'. What I'm trying to say is that the H50 will not give increased clocks compared to the Noctua due to other limiting factors. You might find that the Noctua actually allows for a higher clock as the increase airflow may help to cool down the motherboard and RAM.