Account based voting is always vulnerable to sibyl attacks(multiple accounts) and some people like berniesanders own 50+ accounts. If you use bidbots you can reach 60 reputation without loosing much money.

This is the exact argument of some critics of the current system. That it will basically degenerate into a battle for votes from as many accounts as possible. Today's announcement confirms the big effort in banning v4v attempts.
Im glad you mentioned "investment" because i think one's SP is correlated with his investment in steem, hence its value in any system. Will keep you posted as this plays out 🙂