There was a time before watches turned >43mm when a watch should be 40mm and above because it demands legibility, for example, when used under water; or because of tradition, in the case of pilot watches. In my personal opinion, the nature of the watch should determine size; any other logic is frivolous. Does a plain dress watch need to be 42+?
On the other hand, it is hard to conceive how, and why, ultra thin watches should also hitch this trend for bigness. In terms of proportion, to have something thin and big is ridiculously antithetical. Thin suggests elegance and sophistication; but bigness gives the game away, unless the game is to draw attention.
Personally and against the current trend, big watches--especially those that are big with neither artistic complication nor utilitarian (or traditional) reason--suggest crudeness. I have nothing against a certain brand or watch design but strictly on an impressionistic note, when an associate handed me his 'big-b**g', it reminded me of watches I have seen being peddled on the streets--watches to draw attention or to reassert one's insecure identity.