Welcome to the forum :)
you have a tough decision to make as both the a4 and a4 allroad are nice cars.
The lowest spec a4 avant with the 218ps 3.0tdi, s tronic box and Quattro is a sport model which is approx £36,965
the cheapest a4 all-road with the 218ps 3.0tdi, s tronic box and Quattro is the trim line spec (entry level) and is £38,695.
It depends if you want to spend the extra money on the allroad
In my opinion the allroad has more road presence. I see a white one when I am on my way back from work and it Deffo stands out. For an extra £600 you can have the allroad body kit painted the same colour as the car if you want to make it more subtle.
The allroad has more exclusivity about it and the two models iv highlighted as comparison will drive similar to be honest as the engine power and gearboxes are the same.
Hope iv helped :)
cheers
steve