Acera and Atlus rear derailleurs are a step up from Tourney in construction and longevity. They both perform the same mechanical function. If it's urban riding either they will do nicely. Like all components, keep them serviced and treat them well and they will last (the same can be said for the entire drive chain). For anything other than city cycling then I would look further up the range, Alivio or Deore (Tekking range) if cost is a consideration. I've used Acera and Atlus on 6 to 9 speed setups on commute bikes and the grandkids bikes. Out of personal preference I would use the Acera. Just because something costs more dosen't necessarily mean it will last longer. Neglect kills components...A well maintained gear system of perrty much any quality can run smooth and quiet
