I already had a look at the Red Pitaya, but to me it has quite some issues. First being the gigE interface, this is going to be relatively hard to hook up in a cooperate network, probably requiring one to carry a router. Then there is the price, quite a bit higher than the 159$ student price for the Analog Discovery.
That said, the hardware choices otherwise look better than the Analog Discovery, having SMAs for the probes, the auxiliary ADC/DACs, and the onboard processing grunt needed to do some beefy processing. But, looking at their website and Mjlortons review, the software seems to be a definite weak spot compared the the Analog Discovery, it looks rather immature and simple in places.
All of this wouldn't be such a big deal if the documentation on how to get started coding for the whole Zynq soc would be easy and accessible, because I imagine programming the Zyng as a novice at FPGA's would be quite a challenge, And in this case I don't want to spend too much time figuring out and coding the measuring equipment.
So unless more docs become available on a beginner level, or the software becomes better I personally see the Red Pitaya as a bit of a gamble, and would still like to see if the Analog Discovery could perform in a similar role, albeit at reduced performance, just to get started.