Unfortunately, we didn't have the chance to test the 750 G3 so that I couldn't make any comparison between this unit and the 750 G5. Nonetheless, I included in the comparison charts the Super Flower SF-750F14HG which uses the Leadex III platform (the 750 G3 is based on the Leadex II design), so you can have an idea on the performance difference between the 750 G3 and G5 models.
I don't approve the use of an ACRF topology (you will find more details on this topology by following this link) in this category, from the moment the competition uses superior designs featuring half-bridge (Corsair RM750x and RM750) and full-bridge topologies (Seasonic Focus Plus Gold). This topology is only suitable for budget PSUs, since it requires fewer components of lower cost and it lowers the capacity requirements of the bulk cap, which is among the most expensive parts in a power supply. The 750 G5 uses quality components, and its build quality is high, but its design doesn't allow it to effectively meet the competition in the 750W category. The transient response is one of the most important factors in a PSU's performance since it depicts its operation under real-life conditions where the loads are dynamic and not static. In such scenarios, the G5 cannot keep the +12V deviations within 1%, and the 3.3V rail's transient response is terrible. So although the 750 G5 has tight load regulation and good enough ripple suppression along with a long hold-up time, still it cannot meet the overall performance of any of the aforementioned models.
Super Flower's Leadex II platform, used in the all G3 models, is still a great performer but because of tariff considerations, that line is on the way out. If you want a high-performance PSU, you should try to get one of the G3 models that are still available in the stores. Till the G3 stock clears out, there is no point in preferring a G5 unit. Even when all G3s are gone, there are better options than the G5 (e.g., the Corsair RMx and Seasonic Focus Plus Gold models). Hopefully, EVGA will push FSP to use a different platform in an upcoming G line, or even better Super Flower will move some of its production out of China, and we will see again a Leadex-based G line.
Image Credits: Tom's Hardware
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics, and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.