There are a few things to consider:
The first is more software/hardware - the NRF24L01 uses a proper protocol, is controllable via a library and probably has some handshaking and error checking/correction. I'm not entirely sure what the 315/433MHz ones are, they may or may not include these things, or it may be that they are literally a transmitter and modulator, and you have to provide the data that's to be sent. In terms of implementation it might make it more difficult/challenging, and if you have multiple devices you might not be able to distinguish between the two.
The second is more the nature of the EM waves they emit. Generally speaking, lower frequency means lower power, better penetration, and longer range. So the 314MHz/433MHz transmitters may perform better in situations where there isn't a direct line of sight etc. However, an efficient antenna at 2.4GHz is easier to make on a PCB, so performance may be equal.
One last thing is that as you're looking at *cheap* solutions (i.e. not sparkfun branded), the actual implementations may vary. Someone may have a decent NRF24L01 and get great performance, and someone might have a badly made one and find it's not satisfactory. But I guess that's the nice thing about cheap components, if they work then great, if not then you aren't losing much for them to go in the parts drawer and for you to buy something better. For the project you have described however I would imagine that both will perform well.
I've noticed that dealextreme recently started selling a very cheap NRF24L01 version. (other than displayed) I wonder if they're any good...