"No" is a response to the poll question while "reject proposal" deals with the proposal overall. Maybe you think that some part of the proposal is not appropriate.
"Reject proposal" is more a rejection of the way the proposal is built and presented while "no" is a rejection of what is proposed.
"No" = I do not approve the funding request for the proposed client redesign
"Reject Proposal" = I do not like the proposal parameters, but i might otherwise like the fund request and proposed client redesign
Both a "no" vote and a "reject proposal" vote are negative votes.