Looking to purchase a watch for around 8k for myself. Currently looking at these 4 primarily but can’t decide. I am open to suggestion for other watches around 8k or below. Please let me know if any of these watches should be avoided for a specific reason. I am not really looking g to resell the watch later on so price retention or premium isn’t a concern for me. Thank you.
Those are 4 very different watches with not much in common. One diver (omega), one unique looking do it all watch (cartier), one classic looking chronograph (breitling) and one very unique looking chronograph (tag heuer).
It seems you are quite far from knowing what you want then and maybe should first try figuring out your use case and/or style more.
Personally i am not a big fan of chronographs. So i would probably go with either the omega or the cartier.
The omega is more sporty looking and more resistant. You can truly wear that for any activity, except maybe super fancy clothes stuff. But i would recommend getting it on the steel bracelet instead. Because a bracelet is always the hardest kind of strap option to source after purchase.
The cartier also can be worn to about any occasion, except the most sporty ones. Plus to me it has the downside of not having a transparent caseback that allows you to see the movement. To me the mechanical nature of it is a big part of buying a mechanical watch in the first place. So covering it up with a flat steel plate thag might as well house a battery, kind of defeats part of the purpose. Thats honestly the main thing keeping me from buying a cartier santos.
Between those two it essentially comes down to the following question: are you more likely to jump off a cliff into the ocean or to get fancy box seats at the opera? Because both are suitable for everything inbetween. If you're a cliff diving guy, get the omega. If you're an opera kind of guy, get the cartier.
Other cool options around 8k include: various omegas (seamaster 300, moonwatch, globemaster, aquaterra), various grand seikos (SBGJ249, SBGA413), various IWC (pilot chrono, Portugieser), various carl f. Bucherer (manero chrono or manero flyback).
Personally i went with the omega aquaterra 41mm green dial. Altho its "only" about 6k. I can highly recommend. Its exactly also a GADA watch like the cartier or the Omega SMP you proposed. But kind of covering all the usecases on both ends, a bit more affordable and with the added seethru caseback compared to the cartier.