I have never sinew backed a bow before, but I did harvest the sinew from the buck I took in September. I think the only difference is that the back pieces are slightly longer. It also seemed greasy compared to the leg sinew, but I'm sure if it's prepared properly (some guys suggest bathing it in mild dish soap before drying it), it would function just the same.
If I had the option, I'd choose back sinew just for the longer length.