There have been many literature comparisons between synchronous condensers and STATCOM in various aspects. Contradictory views on response times do exist at the same time because their definitions and corresponding calculation methods fail to reach agreement, and the influence factors of the power grid are not manipulated appropriately. Unfortunately, the response time is an important technical index, which can sometimes be dominant to determine whether the corresponding scheme becomes an engineering application candidate. Firstly the definition and corresponding calculation method are provided in this paper, then simplified and verifiable equivalent simulation systems are established in order to control the grid influence factors, step response times of a synchronous condenser and a STATCOM are compared in details through electromagnetic simulation in three separated fundamental factors. The results show that the synchronous condenser is slightly better than the STATCOM only in the step response of the grid voltage amplitude based on transient response time.