Hi, Patrick
The difference between these two options is that if an email contains multiple links, the former is triggered by clicking on any link, while the latter requires clicking on a specific link to trigger.
For example, I created an email which contains two videos from a video hosting platform. So it contains two URL of the videos.

In the customer journey, if the ‘a link has been clicked’ has been chosen, the person who opens the email clicks on either of the two videos, triggering the Yes branch.

If the ‘following link has been clicked’ has been chosen, there will be a new option for you to choose a certain link.
Only if this video with the certain link is clicked will the Yes branch be triggered.

For your case, what you need to get is the action of clicking a specific button to download.
So you should select ‘following link has been clicked’, and then select the link you need in the ‘Select a value’ option list
If this helped you, I'd appreciate it if you'd mark this as a Verified Answer, which may in turn help others as well.
Best Regards,
Nya