FWIW here is my 2p worth.
I have always been a gadget lover. I am 100% geek.
Prior to April 2015, my 'pride & joy' for the last 6 years was my Rolex on my left wrist. It had replaced my Cartier Santos that I received for my 30th (the Rolex was a 40th present). I kept both, but wore the Rolex 99% of the time.
April 2015 and the Apple Watch came out and I got a SS with a Milanese. I wore them 70%/30% in Rolex favour. Then 70/30 in Apple Watch favour, then 99.999% AW.
Fast forward 9 years and I still have my Rolex and still have my Cartier, but never wear them. I have reevaluated why did I want them and why did I wear them. Mostly it was the joy I got from looking at them, but maybe there was a bit of look at me.
Now, approaching my mid fifties, I realise that I wear something on my wrist for me, not for anyone else. An AW can look classy with the right strap and clothing - as much as the Rolex or Cartier ever did. To me now, the Rolex or Cartier looked good, but didn't give ME as much joy as the AW. And not nearly as useful. Yes, they are a bit of jewellery and will last a lot lot longer than my AW, but given the right strap the AW can be a bit of jewellery as well. Maybe getting older I feel more content in my skin, but I still like the mechanicals, just not enough to replace my AW.
We are all different and have different drivers for things, but I know I would struggle to give up wearing an AW now.
That said, the Cartier won't lose its value, so if you can afford it, get it. If you never wear it, you can always sell it for a good price.