Hmm actually you are correct.

A donkey might weigh about 220kg, and pulls around 4 times its own weigh which comes to about 900kg in total. If tha barrow would weigh around 150kg it leaves 750kg for payload.

Now imagine that the barrow is filled with micro-SD cards, which weigh around 0.4g. The full load will be around 1875000 memory cards. If we take a conservative estimete of using 32GB cards the barrowfull will hold around 60000TB worth of the good stuff.

Now as the donkey might pull the load at maybe 10km/h on a level road, the total bandwidth of the donkey-pulled barrow over the last mile is around 110TB/s. Typical landline DSL downlink might be 20MB/s so the donkey-method is 5.5 million times faster.

---------- edit ----------

Actually I made a trivial mistake here; the units on the DSL are of course Mbits/s and on the cartfull of SD-cards MB/s.
Now if we assume the DSL speed is what you get out-of-the-ethernet port, so that all AAL5 framing and synchronization is not included in it, then it turns out the donkey actually wins more than 44 million times over...