I use both angles, but for different applications.
If you tend to use a chisel to pry the wood out, make them steeper angled, so the edge is thicker. Blasphemy, yes, but in a straight down cut, like a barrel tang or a patchbox opening, I tend to pry at the bottom of the cut. If the chisel is really fine, I can chip the edge.
On the other hand, in light paring or shaving cuts, like a low angle chisel since it takes less effort to push or tap it through the wood.
Tom