With current tech we can't protect astronauts adequately either way tbh. Shortest possible time in space is currently ~1000 days for a Mars trip (thats return). Thats pretty much suicide. Solar flares are powerful enough to knock out entire power grids here on earth...despite us having an atmosphere & being shielded by the earth's magnetic field. In short its a sht-load of energy.
So until we find a way to prevent extra crispy astronauts we're not going to mars. Shouldn't take too long until the tech is ready though.
To answer the question: Return trip will be easier. We can maybe keep someone alive for 1000 days in space soonish...but the rest of their lives is still quite a long way off until thats possible.
There is another solution though: If you can find a way to get there dramatically faster then you can skip a lot of troubles & just accept the remaining risks. For that we'd need something like Mach 100 though...with current tech we can't get a person much higher than Mach 20 safely.
well the mars is larger (thus more gravity) and has an thicker atmosphere than the moon
The moon has no atmosphere.
so after landing you would need a lot of fuel basically a second rocket for them to leave Mars' surface.
Actually ~1/4 of a rocket will suffice (compared to earth launch).