Depends on your perspective but I don't think you can select only one party and expect them to deliver every time. Different circumstances, different approaches, different personalities will sometimes make one party more reasonable than the other.
In Australia our two major parties are called Labor and Liberal. They take it in turns to govern while the splinter parties sit in the wings and whinge.
Rather comically, our Labor Party is no longer a labour party at all but a liberal (small l) party; the Liberal Party has never been in any sense liberal but is a dyed-in-the-wool conservative party who would be quite at home with the British Conservatives or the American Republicans. There are elements of the Liberal Party (prime minister Tony Abbott who was deposed this week among them) who are so far to the right that they would even receive an open-armed welcome from the Tea Party.
Conservatives tend to favour business and frame their laws accordingly; labour governments tend to favour the people and are perhaps less greedy. Who knows, maybe Winston Churchill (or was it Disraeli?) was right when he said, "If you are young and not liberal, then you have no heart; but if you are old and not conservative, then you have no brain."
If both parties do their jobs assiduously, the opposition can usually exert enough restraint to stop the government going too far out on a limb in either direction.
