There's multiple ways to vote for the proposal, so I don't know that I should favor any potential platform for that.
I really hope that anyone who has a significant stake in Steem will take the time to learn how to vote on proposals, in whatever manner they prefer. But I doubt most people will want to do it like I do. I only vote for proposals with the command-line wallet (CLI wallet) because proposal voting requires use of an active key.
I think the majority of people use SteemConnect/Keychain. The ones that don't will know how to do it anyway.