I haven't looked at how many points you get per pound spent but when I used my points to get Legoland annual passes, with Tesco it was the same points cost for adults and children whereas Sainsburys had a cheaper deal for children. So I bought the adult ticket from Tesco & the child from Sainsburys. Does that make sense?
I guess it would help if you thought what you're going to spend the points on and then see how they compare - they seem to do lots of the same deals.