Disadvantages - Mandatory limits are currently unconstitutional. Voluntary limits are not helpful if one candidate does not agree to the limits.
Most candidates are still dependent on the same monied interests as before.
Limits may also make it difficult for unknown candidates to communicate with voters. Candidates who qualify for the same office would receive the same amount of money, thus creating a financially level playing field and allowing all candidates an equal opportunity to reach the voters. It would allow candidates less time to raise money and more time to discuss issues. Disadvantages - Would be contingent on candidates' agreement not to accept or spend any private money. The initial cost is high, which may cause taxpayer resistance.