TPS62843: recommendation of -6 , -7, -8 version for 1.8V or 0.8V?

Tool/software:

Hey!

I see datasheet the -7 and -8  version can output 1.8V 

If I wanted highest efficiency possible, which version should I pick? Same question applies to 0.8vout with the -6 vs. -7 version 

Thank you!