Dealing with the negative polarized

[Raukura Waihaha]

Again all paths are valid.

Sure, from a hindsight perspective, from a foresight perspective, what are your goals? Efficient use of incarnative time/experience, or hang out in the 'well of indifference/denial' for awhile. All roads lead to the same place, but not all contain the same experience. The quality can be deep or shallow.

Maybe STO is shallow due to the faster reunion experienced and STS is a route that provides more contrast and thus, enriches the depth of experience.

I doubt there's a correlation, you can go thru quite a bit of hell on the STO route in 3d, in fact you may end up exploring how STS systems can traumatize as a way of learning STS without actually being STS, and thus helping others making the same perilous adventure. And this experience will carry on in service in the higher densities, especially if you choose to wander.

Why do you doubt the correlation?
Perfection is an unchanging, resting state. This would be the void from where all distortions or fractals of nothing, came from.
So in order to expand one's state of perfection, less than perfect is the only choice available as a means of expansion. It is how we learn a deeper appreciation of something that can't be improved upon.
If some choose to wander and be negative catalyst for others, it doesn't mean they're destined to continue on that path through the higher densities. It could be that they have already been harvested and chose to sacrifice their state of awareness to help others by being the opposite of love, to teach them forgiveness, which is the lesson Ra describes as being integral to stepping off the wheel of karma.

Or you can play it safe in nicer places, helping out where you can, and lead simpler lives.

You seem to equate "nicer" with "more beneficial".
What seems most beneficial to me is providing the creation with a deeper appreciation for it's eternal, resting state.
If this is love and unity as one consciousness, the most beneficial path for the individual who is providing contrast for this state, seems to me to be the opposite end of the spectrum of unity. Otherwise you're doing what you've always done and will continue to sit in a luke warm bath. Nothing wrong with that but it's hardly what I'd call "more efficient". Efficiency finds it's context, in purpose.

I'm betting that ambition in the 3d realm is a reflection of our spiritual character.

I'm betting that some have already learned the fast, STO path and chose to come back to selflessly offer themselves as STS, as a way of deepening their appreciation for what they already know, as well as provide lessons for those who need them. Some may come back as STO wanderers and help by raising the vibration for those who need it also.
The contribution of the STS role is just as valuable as the STO one.