Just like browsing to an international website is slightly slower (although mainly you hardly notice it), mail delivery to an international server will be slightly slower than to a local host. But if your connection speed to the local host is seriously limited, then mail to the international server will still be faster! Of course, one of the main benefits of having a locally hosted server, is that when the international link goes down, your email and website will not be affected.
I must say that having a local provider finally offering uncapped traffic is huge. It will be interesting to see if other hosting providers follow suit. Hetzner increased their local traffic allowance recently, but it will be interesting to see if they respond to Mweb now (they don't generally, but this is a significant change for SA hosting).
