I’ve seen blastoff builds, but not a lot of hermes builds. I think this is because blastoffs are cheaper and smaller, allowing them to be used in smaller, less expensive race cars. But I did a test, to see which is actually better in terms of thrust per energy (idk if that’s a unit but it is now ). I put 2 blastoffs on one side, and 2 hermes on the other. This means both sides have 6 energy being used (3 blastoffs with 2 energy each is 6 energy/2 hermes with 3 energy each is also 6 energy). I centered the mass the best i could, and put a stick in the front so it wouldn’t flip forward when the boost was active. This is the video I made:
The results are that hermes are a better use of energy than blastoffs, because the build turned towards the blastoffs, indicating that the hermes were more powerful thrusters with the same amount of energy on both sides. HOWEVER I must admit blastoffs are still good as well for their compactness and the fact that they are super cheap.
Ultimately, the correct booster depends on the build and how much coin you are willing to spend.