Both good choices and I can see why you are debating. I prefer the AT and would go that route. I can also understand wanting a GS, spring drive, and something differnet than an Omega in rotation. In the end it comes down to which one you like more though? First is aesthetics then technology and brand for me.
I still say the AT even though you already have a few Omegas. There's good reasons you do and why change now especially when the 2 watches are similar in looks but the AT edges out the GS to my eyes.