Which Science 6* to R3

Prentex

I am asking for advice for a rankup decision, so this is the situation:

I have 5* rank 5 sig 200 Cap IW and use him almost every time for questing, aq, aw...
I also have a 5* rank 4 sig 20 Thing, don't use it because i have the 6* rank 2 sig 20
I don't have a 5* void, only the 4 star

My rankup options are

CAP IW unawakened
Void unawakened
Thing sig 20 (mainly for AW defense)

Any input / thoughts are appreciated

Thank you!