I think the argument is that Mint would not need to store the users' raw bank credentials. Yodlee does need to hang on to the raw credentials, but Mint (when they were using Yodlee) only needed to pass them through to Yodlee in exchange for a token.

My assumption was that once Yodlee proved they weren't going away, they could strike privileged deals with banks that obviated the need for screen-scraping, to the mutual security benefit of everyone.