Honestly, I think arguing about build quality at this level is a bit silly. These watches are all constructed in a similar way. There is very little difference, for example, in the construction of an Omega TC-1 and TC-2 and a Hamilton QED. The Hamilton, I think, is even a bit heftier (not that that's an indication of quality). At this level, it really comes down to personal preference in design (and to some extent brand affiliation and marketing).
Here's a photo of an observatory back on a Constellation (in this case, a 1603):
-abe.