"To be into something good" slightly suggests  it happens by chance (you find somebody that is promising relationship...etc), but you feel lucky, you stepped on it.

       Whereas the second would be more by design; you are looking for  a job and find a nice one that you can choose, you are to choose a new friend or relashionship among others, it´s not by chance then.

     In certain contexts either one or the other could be used.