The advantage of using base biasing over emitter biasing?
One major parameter which decide biasing in BJT transistors is Bias Stability. As β (hFE) widely varies from transistor to transistor. An stable biasing will provide minimum alteration in the Q-point on wide changes in β.

Mathematically stability factor is denoted by,

S= delta Ic / delta Icb.

S depends on the circuit configuration and
the bias resistors. S should be as small as possible.

Consider the thress biasing,






Now you can choose a biasing with low value of 'S' for better stability.

We never desire high value of 'S'. If one of the transistor stop working in your design then it's replacemnt may not have the same Beta. You want least effect on the Q-point due to the error in beta value. So need a low value of 'S'. 

Consider these calculations:


VCEQ changes by 41% when β changes by 50%.


VCEQ changes by 25% when β changes by 50%.



VCEQ changes by 6% when β changes by 50%.