Welcome to TRF!
All three watches are very good choices in their own right. Probably, you get most watch for your money with the Omega SM, but you would take a big hit if you want to resell it later. Same thing applies to the Tag Heuer.
Click
this link to go to a comparative test of the SS Sub Date and the Omega SM.
If you want a classic icon of diver's watches, go for the SS Sub Date. You get one of the best movements ever made, the Cal. 3135, most of the ingenious Rolex inventions incorporated in ONE watch, and also a watch that you can get your money back on if you want to resell it later if you just wait some years.
Good luck!