Quantum is better than Classical. Or not?

It is common in literature to read papers in which the need for quantum-mechanical treatment of molecular collisions is stressed, presenting it as a guarantee of accuracy. Often the same authors consider the quasiclassical trajectory method as only suited for qualitative results, or relegated to very high energy ranges. While the use of quantum mechanics in certain conditions is mandatory, its generalized application can bring to paradoxical situations, with expensive quantum mechanical calculations used for obtaining results clearly in the quasiclassical realm without great success, due to the approximations introduced in the quantum procedure for computational economy. Some examples will be shown and discussed, taken from personal experience of the author in the field and from literature, including light chemical species. The aim is to reconcile the use of both quantum-mechanical and quasiclassical calculations, with particular attention to the assessment of the suited ranges of applicability of the methodologies. Exploiting this complementarity can result in an optimal balance between accuracy and computational resources required.