When painting a frame, which type of clear coat do you typically use... 1K or 2K?

It's my understanding that the 2K clear coat is much more durable as it's a two-part polyurethane coating. However, it's also apparently more toxic when spraying (of some concern to me), a little more expensive, and is it perhaps overkill for a bicycle frame? I'm currently painting a steal frame and trying to decide which type of clear I should purchase for when my project gets that far. Note that I'm using spray cans, not an airbrush.