This is a very long comment about why first impression is better than swords dance on this particular set.
First, the Golisopod is holding an assault vest.
Even if it weren't holding an assault vest, swords dance is only good on things that are to survive more than two turns without switching. If it stays in exactly two turns and uses swords dance, it has one turn to attack. It will deal the exact same amount of damage as using the attack twice, and take up a moveslot that can be better filled with something like a coverage move. Seeing how easy it is to activate emergency exit and in two turns or less, which resets the boosts from swords dance, swords dance is not a good move.
In competitive battling, there are Pokemon called sweepers. They often make themselves extremely fast and powerful with setup moves, and once they have set up, they're difficult to stop. Because good sweepers that have good defenses are often banned, most sweepers that people worry about have bad defenses. Thus, a very reliable way to defeat them it to send in a strong Pokemon after its teammate faints, and have that Pokemon use a strong priority move, like first impression. First impression will go first regardless of anybody's speed, and its strong enough to KO most sweepers after it takes one hit while setting up. Because Golisopod has emergency exit, it gets two chances to use first impression without taking a turn to switch out. Thus, first impression is a good move and one of the few signature moves actually worth using.
