Mobile Kangaroo will always install you a new homebutton and calibrate it. Un-authorized repair shops will re-use your old home button that may end up in the button and/or Touch ID (if applicable) not working properly.
The new screen is Calibrated after installation to ensure touch responsiveness and accuracy. Only an Apple Authorized Service Provider like Mobile Kangaroo can calibrate a screen.
A new Proximity Sensor is installed and calibrated on your iPhone. A salvaged proximity sensor does not work properly.
An Apple-genuine LCD comes with a factory-adhered frame. 3rd party installations may cause the frame to separate or lift off just in a few months.
A new Earpiece Speaker is factory installed in your iPhone, unlike unauthorized repair shops that re-use the old speaker. Using a new speaker ensures your iPhone will be able to make the same crisp and clear calls as the day you bought it!
Genuine LCD is always new, unlike 3rd party repair shops that may re-use components. Counterfeit LCDs almost never have the same color or brightness and the backlight may be uneven.
3D Touch is also calibrated after installation. Non-calibrated 3D Touch usually won't work well or even at all on unauthorized screens. Counterfeit parts are more likely to experience dead spots and/or "phantom touch".
A brand new Front-Facing (FaceTime) Camera is factory installed, unlike 3rd party repair shops that reinstall the used camera from the broken screen. Re-used cameras are often not centered correctly, which will affect the quality of your selfies.