Oh...that's all. So let's ignore for just a second the logistical advantages of figuring out how to actually mount a manned mission to build something non-trivial on another body when you're 3 days away, not 6 months away. Pretend that isn't important.
The moon has water, raw materials, enough gravity things don't just float away, abundant solar and we've already figured out how to get people there and back. We already have an MVP to build on.
On the other hand, a manned Mars mission is still an un-funded wank-fantasy with a disturbingly high failure rate for the unmanned attempts.
By your logic, it seems like we should just give up on building any bases in this solar system altogether, and just start building a ship to go to Alpha Centauri.
Obviously 3 days is better than 6 months. A lot more can be done with a shorter window. I just don't think it justifies passing up all the upsides Mars has to offer
On top of that, the Moon has proven mineral resources which can be mined and refined on-site a lot easier than trying to do the same on Mars.
Mars is just too far away. If you're going to neglect distance, then we should just skip Mars and go straight to Alpha Centauri or some other star with a bunch of exoplanets.
If you have a critical failure on the moon, you are home in 3-4 days being debriefed. If you have a critical failure on Mars, it could be 2 years until your remains can be recovered and respectfully laid to rest.
If you're testing a new technology and discover some serious flaw or major way to improve it and lack the materials to make an adjustment you could have that done and sent on the next trip in a week or a month or 3 months from Earth to the Moon. On Mars, you could be looking at 2+ years.
On the moon you have to deal with power over a 13.65 day night, at first this could be achieved by simply having human missions only there for 2 weeks ~ at a time until you get enough power generation there (say a small reactor) to provide sufficient power constnatly. On Mars you have to deal with a night comparable in length to Earth but you have considerably reduced solar irradiance meaning if you use PV it's always going to produce less during the day. This makes the Moon a better candidate for testing power management, battery technologies, small reactors, etc.
Any technology that can survive in the harsher conditions of the moon, will mostly work out of the box on Mars with the only real stuff needing custom-tailored being vehicles as the Martian and luanr regolith will vary enough (especially combined with the gravity differences) to require you to at least adjust suspensions and wheels.
Solar power and batteries should work assuming you're willing to build your base among the "peaks of [near] eternal light" which get sunshine nearly ninety percent of the time.
Mars is better for solar power because you won't need nearly as much battery capacity, as you get light on a ~24 hour cycle same as Earth. The Moon with its slow rotation is much more challenging.
Compress that into a tank and you can chemically (or biologically) convert that into an oxygen-nitrogen atmosphere to breathe.
Is that true? I can't see how that'd be true, unless maybe you are considering aerobraking to enter mars orbit and parachutes for landing on the surface (?)