Bernie got more amendments than anyone passed when he was in the House and he's respected and liked pretty much universally in the senate -- both sides of the aisle. Read about how he worked behind the scenes to get rethug votes for big funding for community-based health clinics in the affordable care act as one example. Meanwhile, she seems to actually be reviled by half of congress, a lightning rod meme of what the right stands against, so they can brag to their constituents how they blocked everything she tried to get through. Bernie's their long-time, good for his word colleague. Plus if he runs he's likely going to have bigger coat tails than Hillary would, meaning more friendly votes in congress. So for getting things done, it seems like night and day. Bernie knows how much he can get through and how to get it. Hillary, not so much. Look at her record.
http://www.alternet.org/election-2016/bernie-gets-it-done-sanders-record-pushing-through-major-reforms-will-surprise-you