if you have just a single distribution needed following a reload, there isn't much difference between a single or two tasks.
A single task will be a bit faster than the two, but overall not much difference.
Multiple tasks will come into their own when you have multiple distributions from the same reloaded QVW, a distribution per department for example, where of course splitting to a reload task and then the multiple distributions is best.
hope that helps
This is just an example:
Imagine that you have two reload tasks for the same document (just reloads). The first one will produce a small version (for example a limited number of years) on tue, wed, thu and fri. The second one will produce a complete version will all data during Sunday night because there is an important meeting on Monday morning. The distribution task will be the same for both (one task triggered by both reload tasks). This way you avoid duplication of the list of users to distribute to.