One of the cardinal strategies of marketing is to be first. This first move gives you an advantage over all possible competitors since you can establish yourself while others play catchup. Likewise, for the public, the pioneer is often the best.
In patents, we can find two types of pioneers: the first one who invents and the first one who patents.
More than one unrelated person may come up with the same or similar invention. In these sometimes not so rare cases, the law may tip towards the first to apply for a patent since the vast majority of countries see the first to patent like the one who should enjoy the exclusive rights to the invention.
Let us imagine two inventors in the same country where the first to patent is recognized as the one who should enjoy exclusive rights. Inventor A is the first to patent, while Inventor B is the first to invent.
As a general rule, Inventor A being the first to patent, would have all the advantages. However, some actions of Inventor B may affect him.
1. Preventing the patent
If both inventors have kept their inventions confidential, the novelty requirement for patenting has not been alternated. Therefore, Inventor A would have no problem filing his/her patent application and acquiring exclusive rights to the invention. Now, if Inventor B disclosed his/her invention to the public before Inventor A filed his/her patent application, the patent application (of Inventor A) will most likely be rejected as not being novel. In that scenario, neither would have exclusive rights to the invention.
2. Defense of prior use
Suppose Inventor B was using or preparing to use the invention (without affecting its novelty). In that case, Inventor A cannot prevent the continuation of that use, even if he/she has the patent granted. Here Inventor A would have exclusive rights to the invention, but limited, among other things, by Inventor B’s prior use.
Even so, it would be more advantageous to be Inventor A, since he/she can enjoy the commercial exploitation of the invention, in addition to freely transferring or licensing it to others.
Therein lies the importance of being the first, the first to patent.