Two identical twins are close to 100% genetically identical (not 100%, but far more than the 99.9% that all humans share). Some pairs may have one twin with higher predisposition for cancer or heart disease or dementia, but their physical potential for the most part is close to identical. So how come identical twins don't always have the same level of achievement, especially those separated at birth? It's because even identical twins brought up in the same household will have different experiences, affecting their intellectual and emotional development and resulting in two distinct personalities that react differently to identical situations.
Droids are sentient as well. The ability to learn and grow from experience is perhaps the key advantage of true intelligence, whether artificial or natural. Droids aren't simply calculators or electronic dictionaries. If a droid has been in combat and manages to live through the experience, you'd expect it to have a higher chance of surviving another battler than a new droid right off the assembly line.
Otherwise, why bother with AI? Why not just equip a roomba with voice commands and a welding torch?