Dress watch conundrum?

Well since you have narrowed it down to these two, for me I will go with both! 🥳 two different styles so both will be great! 

from these two I would pick the Cartier. You may also want to check out JLC. 

You have missed hundreds, perhaps thousands of choices. You narrowed it down to these two. My personal preference is for the Grand Seiko. That may be a tad unfair because I will tend to take the non-Cartier almost every time. The Tank Americaine has cache because Steve McQueen wore one once. That makes it one of three watches that I can think of associated with him.

Elongated tank watches appear to be inaccurate the farther from 12, 3, 6, and 9 that you get. They seem always to be catching up. As a time telling device an elongated tank is a suboptimal design for this reason. Some think that they are pretty.

Fair point. I love JLC, it’s just a bit outside my budget😊

I think the GS is beautiful and the most versatile. That would be my choice. 

The GS I feel will be more versatile, but it's also easy enough to wear Cartier watches with casual clothing.

I'm biased towards Cartier so I'll say Cartier 😂

Since you've got a cartier in your collection, I'd say GS. 

Would you consider a Reverso? 

I was going to say Tank just because it's smaller, but the GS is actually a tolerable sub-38mm case size so I feel it benefits by merit of being less distinctive and thus ultimately more practical. Plus the Cartier crowns annoy me. Somebody calls them ~your grannie's broach on the crown. And they're long and sort of pointy!

GS is more versatile, better finished most likely and can look sportier with a strap change. Cartier is more unique and just pure class imo. I would go Cartier! 

GS all day.  It’s more legible, classic design, and just stunning. In camp rectangular I’m team JLC, not really a fan of Cartier.  Really adore my reverso but equally adore my Grand Seikos. 

Also, I second @Ichibunz, if you can get both, get both!!  I did and I’m a happier person for it 😀

I really like the reverso duo medium but I may have to wait a few years to get one 😂

Cartier

Thanks! That GS is phenomenal. love the 62GS, such a classic.

cartier in my opinion is the best choice but thats my two cents.

Personally, I'd go Grand Seiko. Though to be frank, that one is a bit drab; they have more interesting choices in that design. I tried on the Americaine, and it's very interesting, but I'd find it hard to wear. 

I was looking through some dress watches recently. 

Have you considered Chopard L.U.C XPS? I believe they are fantastic dress watches and the moevement.... ahhhh... 😉

Grand Seiko. 100%. Obviously the tank has the history, but personally, I just don’t like square faces. I know it’s a matter of personal opinion, but it’s just not an appealing shape to me, and Grand Seiko just blows other luxury watches away it terms of the craftsmanship you get for the price, that it makes the brand a no-brainer in my mind.

You are correct. (I still don't care for Cartier, or Steve McQueen, for that matter.)

My vote :)

The SBGW231

I have one so I’m biased - but they are just so damned beautiful and flexible to wear. You will look at that movement in the back regularly and contemplate what an amazing bit of workmanship it is. Just my 10 cents worth - but you just won’t regret it. 

#cartier all day!

Own it, love it!

Normally i’d vote GS but dress watches  in my opinion are something to add a little pizzazz in a collection. so go for the Cartier :)

Definitely go jlc reverso if you want an alternative for the rectangle case dress watch. But the textured faces of a Grand seiko are second to none 

The GS.  I, personally, wouldn't even wear that specific Cartier.

My suggestion:

I have both. The SBGW is more versatile (especially on a light strap), but the Americaine feels special and less common.  The downside with the Americaine is that any strap would need to be custom made, given the small lug width.

I'm a GS fan but of the 2 I'd pick the Cartier, while the GS is more versatile you are wanting a pure dress watch and I think the Cartier is a better option for that.  

I would pick the Grand Seiko. I prefer the reverso for square watches.

Wow. Sell your car get both!