Try to get the pieces of my brain you torn apart with your photo.
Yes 5508 is thinner and seems more classy,
Yes 1680 seems more sporty...
Imho, going to no crown guards
I would go in two other direction,
Wether chase a 6542, because it is pure charm.
The dial(s), the bezel, the thin case, the Domed plexy on some models, and the patina you can get can crush a weak mind ^^.
In another direction, about pure beauty of the oyster and patina, 6610 or 1016 are true killer, a 6610 with a magnificient patina... WOW
While thinking, I realize it is not a question of classy or not.
But imho there is nothing to do with that, it is all about charm.
You can love or dislike a red 1680 just for some patina details or all those kind of stuff.
And the same for the 5508 or other no crown guards sub.
That's vintage, that's pure subjectivity, it is not one type, it is THE model who will catch you.
And when I see the patina of THIS 5508, and the personnality she has, I can understand why it is a heartbreaker.
Best regards
François