I am going to jump in again since I am in the minority.
If you love the watch and think that you will love it for a long time, get the watch.
I love watches but have never been a fan of square faced or roman numeral watches on myself. That's just my opinion. Obviously a lot of people love the cartier watches. It seems like a great fit for a corporate wardrobe. However work wardrobes have become more casual so who knows how you will be dressing in ten years. You may like the cartier for casual wear too, who knows? Or you may only want to keep the watch for ten years.
Through the years, watch trends have changed in size and metals. The watch shown in the Princess Diana image on google seems small to me by today's trends. So that is something to consider.
Next year, the Apple Watch will be available. There are not a lot of fans yet on TPF as far as I can tell, but I see that as the future mobile computer/phone, with a bluetooth headset/mic? so you don't look weird using it to talk. Not that people will be talking on it. People talk a lot less on phones now. I would use it when I'm out at lunch or running errands to check to see if there were urgent messages from work. And for time, calendar, lists, stock quotes? etc. Apple watch is going to totally throw off my jewelry style. So I want to be careful how much I invest in more watches. It may never take off, but look at where we were ten years ago regarding tech and how people now are staring at their phones all day.
However the Cartier could be used as jewelry as well. You can stack it with bracelets and it will look beautiful, whether it operates as a watch or not.
The dbty IMO will look classic forever, simply because it has less detail. I agree you may want a bigger one at some point, but you can always layer.
The watch you can look at and admire. The dbty you'd have to look in a mirror to see. That will affect your enjoyment of the piece.
Also the watch may have some value as a status symbol in your workplace. If co-workers and customers think you are successful based in part on the watch, it could mean more success will come your way. I don't mean that in a shallow sense - it is a very real possibility. Perception is everything.
Get the one you cannot stop thinking about. Give yourself enough time to think about it so that there is no doubt in your mind.
GL! And Congrats!
(BTW, I wear very little of my work reward jewelry these days, except I still wear some of the small pieces.

This is because I bought jewelry I would wear to a corporate job. Now it seems way too fancy, even though they are classic pieces.)