Can anyone please help. I have seen the SPS for sale - it is obviously much cheaper then the XR. Please can anyone tell me what the difference between the 2 is - I believe the XR reclines and the SPS does n't but other then that I can't find any info? I read somewhere that it is narrower? It is nearly half the prce of the XR so will buy it if it does n't compromise on safety? Can anyone please tell me how it compared to the XR in the which tests? Thanks very much