Which updated Haswell rMBP for iOS development?

[Marco L O T]

I am targetting a rMBP for iOS development. I am choosing between the 128GB and 256GB model, and maybe boost to 16GB RAM.
I also want to run a Windows 8.x VM. Only development files will be stored, I will have an external drive for "other files".

Questions:
- Is the 128GB model enough?
- How much space is used by Yosemite?
- Is 16GB highly recommended for a Windows 8.x VM?

Thanks!

EDIT:
This is for the 13 inch models.
I also want to use an external 1080p display in tandem.