I brought my ZR with my friend and he brought the SP together. SP is good for who want a cheaper price, not targeting for a better camera. For SP, you can set the notification LED colors for different apps but ZR cannot. If you think the prize for ZR is reasonable, and you want better battery experience, quad cpu, waterproof phone, replaceable battery, then ZR is a good choice. SP seems a little heavier as it uses metal case I think. One more major difference is that ZR has cover for micro usb and headset plug. It's a little inconvenient but some will take those covers as a plus as they can protect the phone from dust. Also ZR is obviously smoother in my point of view.
All in all, if you don't think price is a major problem and the function of the phone is important to you, then I think ZR is your choice.
Sent from my C5503 using xda app-developers app