Solar and kinetic watches are both quartz watches that recharge themselves instead of using a replaceable battery, but a solar watch charges from light while a kinetic watch charges from the motion of your wrist. Solar is generally the simpler, longer-lasting choice.
The short answer
Both store energy in a rechargeable cell or capacitor and run a quartz movement, so you rarely if ever change a battery. Solar uses a light-sensitive dial to generate power. Kinetic uses a rotor spun by your movement to generate electricity. Different fuel, same goal.
How solar works
A solar watch has a cell under or built into the dial that converts light, whether sunlight or indoor light, into electricity. That charges an internal cell that runs the watch. Leave it near light and it keeps a reserve that can last months in the dark once fully charged.
How kinetic works
A kinetic watch uses an oscillating rotor, like an automatic, but instead of winding a mainspring it generates electricity. That current charges a capacitor or cell that powers the quartz movement. Your everyday wrist motion keeps it topped up.
Reliability and upkeep
Solar tends to be lower maintenance because charging it is as easy as exposure to light. Kinetic depends on regular wear, and its energy-storage capacitor can weaken over years and eventually need service. Both avoid routine battery swaps.
Accuracy
Because both are quartz at heart, they keep excellent time, far better than a typical mechanical watch. The charging method doesn't change the accuracy. It just changes how the watch stays powered.
Which should you choose?
Choose solar if you want the easiest self-charging watch and reliable long-term use with minimal fuss. Choose kinetic if you like the idea of wrist motion powering a quartz watch and you wear it regularly. For most people, solar is the more convenient pick.