You may already know this, I'm sure many do but it's certainly worth saying. The Model 28-3 might be considered somewhat scarce simply because the 28-2 was produced in absolute crazy, crazy volume and the dash-3 production is a drop in the bucket in comparison.
So when it comes to scarcity, the 28-3 destroys the 28-2. That said however, the dash-3 is neither pinned nor recessed, so generally speaking to the normal, average large audience of S&W fans and gun buyers, your model might be considered "less sought after."
Now me, I have a handful of 28-2's, absolutely one of my favorite models ever. I would be quite interested in a 28-3 just for the oddity of it. At the same time, I would keep in mind that to the bulk of folks, it would be certainly less sought after.