exact difference between the two:
gameSpeedData-Normal
incomeGameSpeedScalar 0.15
shipBuildRateGameSpeedScalar 0.10
moduleBuildRateGameSpeedScalar 0.10
shipLinearMaxSpeedGameSpeedScalar 0.30
shipLinearAccelerationGameSpeedScalar 0.30
shipLinearDecelerationGameSpeedScalar 0.30
questCompleteHappinessDeltaScalar 0.0
cultureConnectionReferenceLength 500000
gameSpeedData-Fast
incomeGameSpeedScalar 0.30
shipBuildRateGameSpeedScalar 0.20
moduleBuildRateGameSpeedScalar 0.20
shipLinearMaxSpeedGameSpeedScalar 0.6
shipLinearAccelerationGameSpeedScalar 0.6
shipLinearDecelerationGameSpeedScalar 0.6
questCompleteHappinessDeltaScalar 0.25
cultureConnectionReferenceLength 750000
Basically the difference is in income, culture, build rate, quests and ship movement speed, Which means theres no difference between slow and fast in: how long it takes to do damage once the forces stop moving, how long it takes for antimatter to regen, shields/hull regen..etc. Example: the time it takes for a cap to kill pirate ship x, once the cap starts firing on it and as long as it doesn't move would be about the same in slow and fast.