Is it better to use the collapse clausel or just the parallel for

I am never sure which possibility I should choose to parallelize nested for loops.

For example I have the following code snippet:

#pragma omp parallel for schedule(static)
for(int b=0; b<bSize; b++)
    for(int n=0; n<N; n++) o[n + b*N] = b[n];


#pragma omp parallel for collapse(2) schedule(static)
for(int b=0; b<bSize; b++)
    for(int n=0; n<N; n++) o[n + b*N] = b[n];

In the first snippet I use parallel for (with schedule(static) because of the first touch policy). In some codes I saw people use mostly the collapse-clausel to parallize nested for loops in other codes it is never used instead the nested for loops are parallelized with a simple parallel for. Is this more a habit or is there a difference between the two versions? Is there a reason some people never use collapse(n)?