definitely usagi. Chibi usa is sweet, but she's too bratty and mischievious!

I think both of them have the purest soul.But I've watched that I saw Chibiusais a little mischievous and meany.Usagi is really good to her friends although she is always late,stupid and not clever.

Usagi because Chibi-Usa was Black Lady at one time.

Usagi. Chibi-Usa's soul was too easily tainted by Wiseman. Usagi would never turn into a turncoat princess.

Usagi!

Usagi-chan most likely has the purest soul of the two and it's fair to say Usagi shows a lot of emotion. while Chibusa can be very mischievous at times and at times she won't act very nice..which leads me to say Usagi-chan's Soul is more pure.

Chibiusa was a brat at times. Also she was considerable weaker than Usagi, she turned into the black lady.

Definitely