The Canon PowerShot SX420 IS has a CCD sensor type which is better than the MOS sensor type found on most similar spec digital cameras that came out more than a year ago. CCD sensors produce high quality, low-noise images but consume a lot more power than CMOS sensors. CCD is the most common image sensor type used in digital cameras.
A CCD sensor type is actually the best sensor type amongst all cameras of a comparable type and age to the PowerShot SX420 IS.
Amongst comparable types of camera the worst sensor type is MOS.