First Past the Post or Proportional Representaion

[Ser Clegane]

Proportional Representation gives too much power to the small parties wich are able, in negotiating their voices, to impose their own agenda to the majority. See Israel, France during the IV Republic, and Italy.
It is also a system by nature instable.

You can put certain mechanisms inplace to prevent extreme fragmentation.

E.g., in Germany there is a 5% hurdle that parties have to overcome to be represented in the parliament (alternatively they need to win 3 constituencies).
This way you can avoid having dozens of fringe parties present in the parliament, but you also ensure that a certain diversity of political parties is available for the voters.

Not saying that this is the perfect system to copy - I just would like to point out that there is always a range of options to work with.