We always choose transistors by checking their power dissipation handling limit.

So, we willl calculate V(CE1) & I(C1 max), then we wll calculate P(D1).

And, after calculating power dissipation, we will check the data sheets of transistors, in order to choose the transistor havin power dissipation more than or equal to calculated value.

choosing transistors having higher power dissipation handling factor than required is a good practice.

It also helps us to design the circuits which perform well in worst case scenarios like excess heat dissipation, flow of larger current than expected.