Pathfinder actually offers a couple things over Shape Builder, but they are essentially the same operations.
- You can use Pathfinder to keep things "live" and editable further. This is not possible with Shape Builder.
- Although, admittedly, I think this aspect is overlooked by most
- Pathfinder allows you to perform one action in one click. Shape Builder may require many clicks/drags for the same outcome.
- This is similar to using the Polygonal Tool to draw a shape, or using the Pen Tool. One is simply faster than the other at times.
- Pathfinder tends to create less superfluous anchor points than shape builder operations. Not drastically less, but less.
- With Shape Builder you can often get extra anchors art every shape intersection. Pathfinder, at times, can be a tad smarter in this respect.
And lastly as posted by @13ruce, sometimes it's merely habit. If you learned one way that works, a user tends to stick to that. I still use some very old methods for things merely because that's how I learned and have worked forever.
- Perhaps more imperceptible, but Pathfinder causes the user to think in terms of start/end rather than start/process/end. I find it is sometimes easier to see where you want to go and merely get there with a click after setting up shapes as I know they need to be configured. Shape Builder can cause some undoing and rethinking about how shapes are interacting in order to get to the end. It's really more of how the user thinks as opposed to any specific tool features.
I am often glassy eyed when I see a newer user perform some action in a totally different manner than I'm accustomed to. A good example of this is Live Paint. I learned AI long, long before Live Paint was a thing. So I don't rely on Live Paint at all. I could, but it doesn't really speed up my process. That doesn't necessarily mean my method is better than any Live Paint method, or that Live Paint is better than my method. They are merely different.