The numbers in the piecewise polynomials can get quite large; the numbers in the B-spline basis range between 0 and 1. There are many more zeros in the B-spline basis. Interchanging SPLINE, BSPLINE, ...

Using cubic splines is also feasible and more attractive under multiple shape constraints; computing the optimal spline smoother is then formulated as a second-order cone programming problem.

Kate Tilling, Corrie Macdonald-Wallis, Debbie A. Lawlor, Rachael A. Hughes, Laura D. Howe, Modelling Childhood Growth Using Fractional Polynomials and Linear Splines, Annals of Nutrition & Metabolism, ...