Since Piloswine and Mamoswine are physical hitters, it learns Earthquake at lvl 40 or 46, which ever one P3D goes by. So it would be best to evolve it as soon as it learns that move.

Is Piloswine better than Mamoswine?

For the Great League, Piloswine actually has a better stat distribution as you can squeeze in more bulk (and thus, more TDO) due to the fact that its attack stat (which inflates its CP) is not that high, as you can see in the comparison below (both share the same exact moveset, but Mamoswine also has access to Ancient ...

Is Piloswine a good Pokemon?

As part of the Ice-type conglomerate, Piloswine benefits from Avalanche with decent bulk and Atk. Its DPS is comparable to that of Articuno's. It was once a top-pick for Ice-type damage, and an amazing counter to Zapdos raids in particular, but it's been completely overshadowed by its own fully evolved form: Mamoswine.