When it comes to power meters, there are a few key factors to consider: accuracy, reliability, compatibility, weight, battery life, and ease of installation.
The 4iiii Precision Pro 2 is a pod-based power meter, while the Shimano FC-R9100-P, SRAM Red AXS, and Quarq DZero are spider-based. The main advantage of the pod-based design is that it's easier and less expensive to switch between different cranksets and groupsets. However, some cyclists may find the pods to be less aesthetically pleasing.
In terms of accuracy, all of these power meters are highly accurate, with the 4iiii Precision Pro 2 boasting an accuracy of +/- 1.5%, the Shimano FC-R9100-P and SRAM Red AXS having an accuracy of +/- 1.5%, and the Quarq DZero having an accuracy of +/- 1.5%.
Reliability is also similar across all of these power meters, with each one being built to withstand the rigors of daily use.
Compatibility-wise, the 4iiii Precision Pro 2 is compatible with a wide range of cranksets and groupsets, while the Shimano FC-R9100-P, SRAM Red AXS, and Quarq DZero are more limited in their compatibility.
When it comes to weight, the 4iiii Precision Pro 2 is the lightest of the bunch, weighing in at 35 grams. The Shimano FC-R9100-P and Quarq DZero both weigh in at 100 grams, while the SRAM Red AXS is the heaviest at 120 grams.
Battery life is also similar across all of these power meters, with the 4iiii Precision Pro 2, Shimano FC-R9100-P, and Quarq DZero all boasting a battery life of around 100 hours and the SRAM Red AXS having a battery life of 60 hours.
As for ease of installation, the 4iiii Precision Pro 2 is the easiest to install, as it simply attaches to the crank arm. The Shimano FC-R9100-P, SRAM Red AXS, and Quarq DZero, on the other hand, require more involved installation processes.
Overall, the 4iiii Precision Pro 2 is a great option for cyclists who need to switch between different cranksets and groupsets, while the Shimano FC-R9100-P, SRAM Red AXS, and Quarq DZero are better suited for cyclists who are looking for a more traditional spider-based power meter. All of these power meters are highly accurate, reliable, and offer similar battery life and weight. Ultimately, the best power meter for you will depend on your specific needs and preferences.