Which is kind of absurd. Both have long histories of political involvement from an early age, and Sanders has plenty more years in elected office. The idea that she's more experienced can only have two real basis the way I see it. First, that she's been closer to the presidency and is more experienced with international diplomacy, and that's a legitimate argument. But otherwise... the major difference is her political career looks more like what's expected of a high-level politician. Yale student. Recognition in the right circles. Gained favor with high-level politicians by working on their campaigns. Served on Wal-Mart's board of directors through their most infamous years...
Looking through Sander's history, it's pretty damn extensive, and it looks to me like he has a lot of experience and success fighting against the mainstream political grain of both parties. Reading through his history right now... it's damn impressive that he won his first elected office while describing himself as a socialist in 1981. And has apparently has plenty of well-regarded accomplishments under his belt in Vermont that went against popular politics of the time. And he self-describes this stuff as his understanding of how to motivate people at a grassroots level, which has apparently been his thing since childhood (Wikipedia: "He has described himself as a mediocre college student because the classroom was "boring and irrelevant," while the community provided his most significant learning"). So all this talk about him not understanding what he's saying when he talks a big fight against the political climate seems to be ignoring his history. And it looks like he doesn't just pursue every fight he can with blind ideology, either (Wiki: "In March 2006, after a series of resolutions passed in various Vermont towns calling for him to bring articles of impeachment against George W. Bush, Sanders stated that it would be "impractical to talk about impeachment" with Republicans in control of the House and Senate.").