Difference between Astral Projection and Window

[Chazar]

I am bit short of time to try, and a search didnt reveal much: What is the difference between AstralProjection and AstralWindow?

From the description, I would only say that the Window costs one pearl (and path) more for the sole benefit of not endangering the caster. Is there anything else? How long do these spells Last? Can the caster used for something else in the next round?

Thanks!