If we're going to include "finishing" in the equation then design very much needs to be involved
I think I just mean the quality of the finishing/execution of the intended design, not how much
design intricacy there is.
For instance a simple 3 link oyster bracelet is exactly that: simple. But you can have some with rougher edges, some with crisp but not disruptively sharp or coarse edges, and then others that actually have a bit soft edges just from unskilled/inexpensive brushing. Also there can be a large variance in how tight the tolerances of joined 3 links are, and how long those tolerances last. Huge variance can exist in something as simple as a 3 link oyster style bracelet from one company to another and from one price point to another, from one price point to another.
So that's what I mean in terms finishing and construction.
And based on that criteria, from my direct experience of owning both brands and many others, both my 1999/2000 Tag and my 2016 Diver 65 are of a quality on par with my BB58 or SMP. I'd be tempted to say that they're better than my early 90s Rolex stuff, but those have so much mileage that it's not really a fair comparison. Especially the bracelet which has hollow center links and is starting to develop some play. But it has an extra decade of use even over the Tag haha. Time will tell how well they all hold up after 30y. But the Tag has remained impressively tight