In the slow scenario an alien civilization would let humans do the work. The aliens would go about their business until we reached a point in technology and exploration when we discover their presence, most likely through some detectable signature of technology. A wait and see approach would allow humans to digest the idea of extraterrestrial intelligence. It would likely take many years of research to determine the nature and meaning of a signal discovered coming from far-off space. That might create enough pressure for humans to finally build a framework for responding to extraterrestrial intelligence diplomacy needs. Diplomacy doesn’t have to mean being to being contact, it can just as easily describe the formation of messages to send to a far-off extraterrestrial civilization. The time would allow humans to process the news that extraterrestrial intelligence exists in a calm and rational manner, because there is no immediate threat. At some point, the watchful extraterrestrials could then decide it’s time to say hello by sending a detectable signal with a specific message. The relationship could develop from there.
The slow method could also cause issues with human trust. A signal based approach relies on scientific groups and probably governmental leaders to do the work. How much transparency they choose to have in the process would probably be determined by the group of scientists making the discovery and the nature of the government of the country in which the discovery is made. Most scientists believe in the open sharing of information for the advancement of science. Any attempts by governments to control such a discovery would probably be met with leaks to the media. In some countries, with tight controls on their scientists, leaks might not occur for months or years. No matter what the scenario such information once revealed would be viewed with a fair amount of suspicion from others on the planet. Are you really telling us everything? Are you collaborating with aliens to gain some form of advantage? It could set countries against one another and that could lead to serious conflicts.
In a fast scenario the extraterrestrials could send representatives to our solar system. Perhaps they would still want to signal an introduction first. This would allow a brief time of consideration by humans, before the dramatic event of physical First Contact. The fast approach has the benefit of capturing the complete and total attention of the planet at once, in a way that would have far more impact than the slow method. One would imagine that aliens considering such a thing would do so for a reason. It could be that they want to see us join together as a civilization. Perhaps they are concerned about our environmental problems.
The primary downside to the fast method is threat. Any physical extraterrestrial presence in our solar system will be perceived with some degree of threat, not matter how friendly or welcoming the extraterrestrials may be. Fear and negative reactions could be the by-product of perceived threat, and if the situation is not carefully managed it could lead to chaotic situations here on Earth.
On the positive side, a dramatic and fast First Contact event could bypass all of the entanglements of the scientific process and government intervention. It could be conducted in a way that was designed to reach all of the people of Earth in an equal fashion. It could be done with great transparency and openness. This could mean less conflict between nations and an actual joining together of nations in response. From this writer’s perspective, this approach would have great advantages in the long-term human response to First Contact.
Of course, it all goes back to motivation. We can speculate all we want about extraterrestrial motivation. We won’t know until First Contact occurs, if it ever occurs at all. I think there is one thing that we can agree on: any extraterrestrials making the effort to say hello will have a motivation of some sort. What they hope to accomplish may decide the method they use to the make the introduction.