When to use
The only time it is ever 'advised' to use the entire move, is if the first hit connects while the opponent is backed up against a wall, as this is the only time all six hits will be able to connect. However, the move is highly punishable, as the 1 following f,f+3 has to be buffered, meaning that if the f,f+3 is blocked, the opponent can simply duck under the first left punch and punish with a WS launcher followed by a juggle.
Using only the f,f+3,1 part of the string, i.e. the first two parts of the move, can lead to decent juggle setups, each taking roughly one third of the opponents health bar. But again, as the 1 has to be buffered, it is a highly punishable move if the initial kick is blocked. This is why it is important to mix up f,f+3,1 with a regular f,f+3 followed by a quick mid-hitting attack, just to keep the opponent on their toes.
Using only f,f+3, however, is a good option, because it puts Jin at a frame advantage on block, so Jin can start a low/mid/throw mixup. Also, f,f+3 is the only launcher Jin has that is safe on block. However, it is a bit slow-ish and can be sidestepped easily.