What i found was that you have a great advantage attacking from any of these tank positions (red ones) as that makes you see the enemy tank before he can see you, while its the opposite if you meet a siege tank from the direction where there are no tanks, then you will be shot first and most likely lose if you got even numbers.
Ghosts in picture got sight range of 11 (ocular implants), one more than the tank but still they died as you can see right/bottom right where there should be ghosts (and tanks) in a circle. The spots where ghosts still survived are where they stand and saw the enemy tank first.
This is the same for any unit so if you got the same sight range you have a clear advantage from getting the information first, and as you can see not even +1 sight range makes a difference sometimes.
From my testing the absolute worst direction to scout from is East. You could walk tanks very far before getting a glimpse on center blue tank.
(all these tanks + ghosts can see blue tank but not vice versa)
(All tanks here have seen the blue tank then moved away until it cant see it)
(Blue pov from above same position, tanks that can be shot even though they walked back to not see blue tank, the tanks here are invincible which is why they werent shot at, the above image shows mortal tanks that were shot and had to move back one step, thats why there are tanks way farther than these ones)
(This Turret got sight range 11 vs tanks 10. It should be able to see all tanks in all directions that is currently watching the Turret)
If you play as Zerg and use Overlord scouting (duh!) it has sight range 9 vs Command Centers 10. Then you would want an angle of scouting from top left.
(As for vs Protoss ure out of luck)