Testing if a point is inside a convex hull can be done in a variety of ways. Inhull converts the problem into a dot product. If not supplied, it also computes the convex hull too. Inhull also attempts to avoid memory problems, doing the computation in smaller blocks when appropriate.
Here is a comparison of inhull to tsearchn:
n = 500;
m = 100;
p = 5;
xyz = rand(m,p);
testpts = rand(n,p)-.1;
tess = delaunayn(xyz);
in0 = ~isnan(tsearchn(xyz,tess,testpts));
in1 = inhull(testpts,xyz);
tsearchn: Elapsed time is 0.813646 seconds.
inhull: Elapsed time is 0.242993 seconds.