i tried both the artillery route (not for space racing, for the unit!) and the flight route.
I found artilleries to be very strong, but coming a little too late.
The good thing is they upgrade catapults and cannons, and need no ressource (cannons require iron

).
The bad things are
- the tech is expensive (4000 beakers, needing physics, rifling, steel)
- the movement is slow,
- the unit is not really cheap (150 hammers).
So, if you're not in a dominant position or gunning for spaceship, artillery won't save you. + the AIs beeline to it, so the tech often has no trade value.
OTH flight isn't giving you the edge easier.
- You need oil to build fighters.
- flight tech is 5000 beakers requiring combustion (which requires railroad, which requires steel and steam power which requires replaceable parts) and physics. So it's even more expensive.
But in some way, it's more straightforward: you need combustion if you want transports don't you? Rifling isn't as highly needed, thoug useful.
The good part about the flight route :
- you can build airports = more commerce + fast reinforcements
- fighters are cheap (100 hammers), they don't die often, they don't need promotions = you can stedily build up a huge force, even low hammers cities can build a fighter
- fighters can rebase in 1 turn, whereever they are
- they can hurt naval units
- they can do recon
- they can bomb cultural defenses.
- you can go on researching to bombers while building those airports and fighters
The bad part :
- fighters/bombers can't kill any unit = you need assault troops. The best assault troops to send after a bomber are... artilleries

- fighters/bombers don't defend themselves on the ground = you need to defend the city they are in.
- you need oil
- more troops = more upkeep
- it's tedious to send fighter after fighter attacking.