Their are upsides and downsides either way. Moving the coalition-building to before the election, as the US and (to a lesser extent) the UK do, means that voter

Their are upsides and downsides either way. Moving the coalition-building to before the election, as the US and (to a lesser extent) the UK do, means that voters have a pretty good idea of the final outcome they're voting for. On the other hand, keeping the coalition-building until after the election allows voters to send a stronger signal about which particular part of that coalition they're supporting, which arguably makes it easier for parties to evolve in response to shifts in the electoral climate.