@lewm , +1
That said, I have both and use Wallys far more often for my 5 tonearms. Well, actually I have the UNI-Pro but same idea. If p2s is exact, which really ought to be a given, especially if you have the right tools and set it yourself, I find the Wally to be more precise. I like arc protractors because alignment can be checked anywhere along the arc rather than at a single point, a la Smart/UNI Pro; and Wallys are the best arc protractors I’ve found. The originals anyway; I’ve never tried the new ones.
But they’re both excellent, so like Lewm said, don’t overthink.