Either way, Sep, just to let you know. Den isn't going to go through with turning to the "good" side unless he can get something out of it. While he is swaying part of the crew, and trying to get the rest of it to his side, That isn't to go against Palpatine. He needs to know and understand his troops anyway to efficiently know how to use them. So while there may be a light threat to defect, Den is very happy in the Empire and plans to stay and get more out of it.

With the Empire he is rich and can gain many things easily by merely kissing ass at this point.

With the Rebels, well, it seems doubtful they could even get reinforcements so risking his life, his ship, and the crew, has no benefits.