We can try some empirical observations, though, in the absence of a properly controlled long-term experiment.
Centralis, Lycanthrope and Rodentia Petram are all 50,000 population extraction economies. Centralis is run by a very active BGS group which regularly encourages explorers to sell data there ... the other two are looked after but by much smaller groups. The first two have been populated for 6 months, with RPet having been inhabited a bit longer. Lux Caeli is a 4th 50,000 population Extraction which has been set up so recently it doesn't have the system name in game yet, does not show any signs of active attention by a player group, and has extremely low general traffic levels.
So, we would theorise, given this, that Centralis would have the best outfitting, with Lycanthrope and RPet being somewhere between that and Lux Caeli.
(The outfitting monitor for these stations is on a "never remove" policy, so fluctuations in stock levels should not affect the observations)
Centralis:
https://cdb.sotl.org.uk/stations/90/outfitting
Lycanthrope:
https://cdb.sotl.org.uk/stations/86/outfitting
Rodentia Petram:
https://cdb.sotl.org.uk/stations/28/outfitting
Lux Caeli:
https://cdb.sotl.org.uk/stations/106/outfitting
What we actually see:
- RPet and LCaeli have basically identical outfitting to each other. There's a very small difference in what ship armour is available - RPet has Hauler, LCaeli has Viper IV.
- Centralis and Lycanthrope have almost identical outfitting (which is pretty consistently worse than the first two) ...
however, Centralis has two D-rated modules available (hatchbreaker 1D, 3D and shield generator 2D, 3D) whereas Lycanthrope does not.
To add more information, there are 4 other 50,000 population Extraction economies which were settled earlier ... all have had some BGS attention but I don't know how much:
Signalis and Far Tauri: Centralis/Lycanthrope template, but with slightly different ship armour
Kopernik and Aurora Astrum: Centralis/Lycanthrope template, but with the same D-rated modules as Centralis
...
Conclusions so far? Not a lot. It looks like economy+population isn't the sole decider - RPet and LCaeli have better outfitting despite otherwise being identical in those respects. There is a difference in that RPet and LCaeli have democratic governments, whereas the others are a mix of 3 Cooperatives, a Prison Colony, a Dictatorship, and a Theocracy. Kopernik and Aurora Astrum, which also have the D-rated modules, are the Cooperatives...
Government + population may be a more relevant factor. Compare:
https://cdb.sotl.org.uk/stations/107/outfitting (Industrial, Confederacy)
https://cdb.sotl.org.uk/stations/83/outfitting (Industrial, Confederacy but was Dictatorship with Social ethos)
https://cdb.sotl.org.uk/stations/19/outfitting (Industrial, Dictatorship)
Now, remembering that the monitor is on "never remove", I looked up a recent EDDN record for Marigold City -
https://ross.eddb.io/eddn/log/12018654 - and that is just the typical Confederacy template to match its current government.
(I should really make the monitor reset if the station changes hands, then...)
...
So, based on this, I think:
- what sort of modules are available in outfitting is primarily based on
government, all else equal. (Corporate governments seem to be generally better, or to a lesser extent Democracies ... though if you want weapons, go Feudal)
- exploration data, or indeed general BGS activity, appears to have very little effect on causing improvements to outfitting ... [1]
- economy and population may push a station up or down the scale, but perhaps not directly - as far as I can tell, every single station ICU Colonial Corps control has almost identical outfitting, despite having a mix of economies and a factor of 10 in population. More likely the effect of these is indirect - outside of Colonia in the procedurally-generated systems of the bubble, these may result in a range of "system tech level" values based on the economy and population, which then go on to affect the outfitting ... whereas Colonia's might be more consistently set.
[1] There is one exception - Taras Shevchenko Hub has considerably better outfitting than every other CEI-class settlement.
https://cdb.sotl.org.uk/stations/61/outfitting
No idea why and I don't think it fits with a general BGS activity idea.