Seems there's a lot of variables although it's unclear why. You have 318d vs 320d, Saloon vs Touring, M Sport vs Sport. How come you are left with just two choices here?
Anyway, it seems like a "performance vs practicality vs performance" question (assuming you count the 320d as a performance engine - and I have a 320d so I mean that without any irony).
For me, the engine/performance is most important because, ultimately, it's how you feel from the driver's seat that defines the experience, not how the car looks. The 320d wins hands down there for me so I'd go for that.
However, the decision is muddled because it's not 318d vs 320d but 318d saloon vs 318d touring. I haven't driven the touring but I'm sure it loses a little to the saloon in performance terms so maybe that balances the 318d vs 320d side of the equation? Can you not have the 320d saloon as an option?
As it stands, I'd say neither car is 'better' than the other - they are simply different, so it comes down to your priorities in the "318d vs 320d, Saloon vs Touring, M Sport vs Sport" debate - assuming you really only have two choices!
Drives: F30 320d Luxury. On order: Glacier Silver 430d M Sport