Earth, because I live here. Runner up is Venus, though. I think it’s a more viable (but still incredibly hard) solution for permanent colonization as it has similar gravity and size to Earth and a more substantial atmosphere. Like Mars, it would need incredibly massive reworking to create permanent settlements, but I think that will be somewhat “easier” to do on a planet with similar gravity.
Earth, because I live here. Runner up is Venus, though. I think it’s a more viable (but still incredibly hard) solution for permanent colonization as it has similar gravity and size to Earth and a more substantial atmosphere. Like Mars, it would need incredibly massive reworking to create permanent settlements, but I think that will be somewhat “easier” to do on a planet with similar gravity.