Yay. Someone said it.

Get the demo versions of both and play around with them. 
 
I think that Diva is the best virtual analog emulation I have ever heard.
 
I think that Zebra is off-the-charts amazing, and can probably create just about any synth sound you could need.  They even give away a free one oscillator version called Zebralette, that is a decent synth in it's own right!
 
If I need to buy another synth, it will be Zebra.  They have a dinosaur discount of $50 if you send in a picture of your vintage gear

Just get both. Buy one first and then save up for the other. Then get that. You'll love them both.
 
And yes, Omnishpere is the best for dreamy unheard of stuff ;)

Couldn't do without either of these synths, if you buy one you will probably end up buying the other anyway :)

Well thank you all so much for the replies. Zebra it will be
..........next Omnisphere .......... then Diva ................. then Falcon
......Flutes of Fire to top it off 

personally i would go with zebra. i love the semi modular approach with zebra and it can do far more than diva. however you will never get a sound out of zebra quite the same as you can with diva.
diva is possibly my favourite VA synth ever, but zebra can do so much more