Bernie Sanders not using a SuperPAC makes him look more authentic and as someone who answers to the people. It also helps him contrast from Hillary Clinton and large donors. Having said that, it may be foolish. My personal opinion is that it will backfire, especially in the general election. But it could be enough to propel him through the primary. The problem is it will likely eventually catch up to him in November if he gets the nomination.
Bernie Sanders has every advantage over Hillary Clinton in the mind of anybody with a minimum level of intelligence. Not having a PAC is only one, but not nearly the most important, of Sanders' advantages over this woman. Keeping in mind, however, that this still does not make Bernie a good candidate, just Hillary makes him look that way.
While it plays well with his voter base, in the long run not having a SUPER PAC is not an advantage for Bernie. Not having the ability to spend larger amounts of ad money in the primaries on Super Tuesday is going to hurt his name reconization with the majority of voters.
The fact that Bernie Sanders does not have a super PAC supporting his campaign may gain him a core group of supporters who do not like the way that campaigns are financed by big businesses and Wall Street. However, ultimately this will mean that Hillary Clinton will be able to outspend him at every point of the election, which will always give her a sizable advantage and perhaps the Democratic nomination.