The short answer is no, there is no difference between servers on the Free plan and the Pro plan.
We strive to ensure that all our servers are located in the best datacenters in any given region and are using the best routing and bandwidth available.
The primary difference between paid and free servers would be the number of active users connected the server in question. As you can imagine, since we have more free users than paid, the free servers will have more users connected to them than the paid.
However, this is something we're managing on a daily basis. We monitor the usage of all our servers and if we see the demand for more in a specific region, we will add more servers there to accommodate our customers' needs.