Well it depends. If human will move to Mars, do they really need not to lose their bones strength and so? If people on Mars will keep 1/3 of what their body compared to Earth because there is about 1/3 gravity, they will be fine for Mars becausee they adapted. But they won't be able to come back.

Venus gravity is just little lower than Earth's but that mean it is harder to land same amount of cargo there (compared to Mars) + you are definitely not coming back because of it anysoon.