The phrase "deciding factor" refers to the one thing or situation that determines the outcome of a particular decision or event. It is the most important element that influences the final result. Full definition
The bottom line: your resume design may just be one of the most important deciding factors in whether or not YOU get the interview over the hordes of other job seekers. (distinctiveweb.com)
The major deciding factors when choosing company training versus private training are your finances and your preferences for training. (truckingtruth.com)