This follows the same style of analysis as https://forums.galciv2.com/?ForumID=346&AID=116303
Basically I compare weapons within the Mass driver line. Newer tech weapons should have higher Damage/size ratios, given that they cost more monetary speaking as well as the research points invested.
I compared all the weapons across all hull sizes from tiny to huge , and at 3 arbitary miniturization sizes 0, 40% and 115%.
Interestingly enough Quantum drivers I , II appears to be worse off compared to Graviton driver IV for almost all hull sizes (altough quantum drivers III is always better than II which is always better than I) , across all miniaturization sizes. The only exception seems to be huge with 115% miniaturization where Quantum drivers II is a touch better than graviton drivers IV.
For Quantum drivers III
At 0% miniaturization
Tiny to medium hulls, Graviton drives IV is strictly better.
At large hulls, Quantum drivers III starts to look better than Graviton drivers, though the different is minor (0.004).
At 40% and 115% miniarutization
Medium hulls becomes the crossover point where Quantum driver III starts to look a little better than Graviton drivers IV
There is also a rather small dip for tiny hulls and little miniturization, between Singulariy driver IV and graviton driver I, but I doubt that's too significant.
Conclusion:
Quantum drivers I and II are almost always worthless compared to graviton IV.
Quantum drivers III become useful when you start using miniaturization and medium hulls and above. But I suspect, given the extra research and $ costs, Graviton drivers IV is a good spot to stop at researching.
Or if you want to research past it, research up to HD Spike driver which is significantly better than Graviton drivers IV.