I didn't edit my previous post because it seems I made some false assumptions up there, so rather than edit I prefer to do a new post in order to avoid confusion...
The way I see it: The APC40 was the de-facto MIDI controller for Live 8. Push is the de-facto MIDI controller for Live 9.
I did some more studying on the Push today because I think its a very interesting piece of hardware. I can now also safely say that what I said above is wrong.
The APC40 is a Live controller, Push is a Live instrument.
Two different devices, two different purposes. You can't compare them one on one because both devices do totally different things. The APC controls Live whereas the Push plays Live.
I don't think the OP should ask himself which one is better in order to decide which to buy. I think the better question is; "which should I buy first?".
Now, I do wonder how much extra you could do with Push when you throw M4l into the setup