The Atmos and the 4D are the same cart, the omega has the same nude body style but I do not think it is strictly the same cart.
That said I have not heard the Omega but have heard the bloom, yatra and atmos and love/d them all. The S designation on the cart means it has silver wire for the coils. The Zyx carts seem to sound best in the standard copper version with the silver sounding less immediate/veiled and the gold being the worst and most expensive option.
I'd likely pass if it is a silver coil version but YMMV