I want to establish a wireless network in a small town, distances around 3km.

What is for me the best solution WDS(roaming) or AP with backbone? What is the big difference?

In my backbone solution every AP will have a omni to reach clients with laptops and a flat one to connect to the other AP.

I think the big difference is only to have more quality of signal in the AP's not connect to the ethernet, am I right?