In terms of aesthetics, what is the best type of crown for a tooth, lava zirconia?

Consult your dentist. It is important to discuss the individual patient's needs for the type of crown with the dentist. Needs vary based on not only aesthetics of the smile but also on the function of the tooth involved. The health of the gingiva or gum may play a role as well as the height of the remaining tooth. I work with dental colleagues in the treatment of cleft lip and palate patients but am not a dentist.
Not zirconia. Zirconia is strong, but not esthetic, so it is often cut back and layered with feldspathic porcelain. Then you lose the strength you were seeking. If you need high strength, i prefer e.Max lithium silicate porcelain. It is beautiful and strong. And i prefer computer milling to pressing. If strength is less important, i like to, use empress multi-layered blocks or feldspathic porcelain.