I'm confused about one of the core principles of Bitcoin. When various nodes are confirming transactions, why does the longest block win out? That is, why doesn't the system allow whoever confirms a transaction or group of transactions first be the block that all the other nodes accept? I realize there has to be some logic in the situation where two nodes submit confirmations at the same time, but what problems would get introduced if the node that confirmed a group of transactions first, regardless of the size of the block, win?
The problem here lies in a misunderstanding. It's not the longest block that wins out, but the longest blockchain (read "the blockchain with the most cumulative difficulty"). The length of a single block is hereby irrelevant and in fact usually the node that first confirms a set of transactions wins.