Whether lithium grease or silicone is better will depend on the application.
Lithium grease is better for it's high viscosity and water resistance as well as it's ability to withstand extreme temperatures which makes it better and suitable for lubrication of metal to metal components.
And silicone grease is made of silicone oil and a thickening agent that makes it great for adhesion to various surfaces, including plastic and rubber and is also good for and known for it's water resistance and it's resistances to fluctuations of temperatures.
Lithium grease will dry out and can destroy plastic and silicon on metal won't hurt it but the lithium will last longer on metal parts.
Lithium grease does harden overtime, especially white lithium grease. as a result of oxidation, base oil evaporation and the fluctuation of temperatures.
The extent of the hardening of the lithium grease can also vary depending on the specific grease formulation and usage conditions.
White lithium grease does get hard overtime and dry out, especially when the white lithium grease is exposed to air and heat.
When the white lithium grease gets hard it can actually get as hard as cement and cause issues such as jamming of things and seizing of the things that it's supposed to be lubricating.
White lithium grease was used in the 50s and 60s for lubrication of seat rails by automakers but over time it can dry out and harden and jam the seat rails and other mechanisms.
There is a difference between lithium and white lithium grease.
The main difference in lithium and white lithium grease is in the appearance and their use in certain applications.
Regular lithium grease can have different colors depending on it's formulation.
And white lithium grease may also have added ingredients like PTFE or Zinc oxide for water resistance and other certain purposes.
White lithium grease is often used in applications that require resistance to water, protection against corrosion and in places where a cleaner and more visible grease is needed.
Examples of some white lithium grease are CRC White lithium grease and WD-40 Specialist White Lithium Grease.
white lithium grease is also commonly used for sunroof panels, door hinges and other applications in which water and corrosion are a concern.
Regular lithium grease can be various colors including red and brown depending on the additives.
Regular lithium grease contains lithium soap which is the thickening agent and the base oil of lithium grease is often mineral oil.
Regular lithium grease is used for general purpose lubrication and protection against wear and tear such as in bearings and other things that need protection against wear and tear.
Examples of regular lithium grease are red lithium grease and other general purpose lithium grease formulations.
Lithium grease of the regular kind if commonly used in cars, heavy machinery and other applications in which a robust lubrication is required.