It's possible to infer that the best option for a Democratic system of government is to have full disclosure on the financial holdings of the members of the Congress.
Transparency helps people understand and follow where money goes around the government. Having Congress members make full disclosure of their financial holdings would make it easier for the population to follow on the growth of their fortunes, which could give a red flag if someone multiplied their fortune in short period of time, for example, which could have been made possible via corruption.
Transparency and honesty are important values in nowadays politics, and having Congress member make full disclosure of their financial holdings is a step in that direction.