Oh yeah, an insulated equipment grounding wire or grounding electrode conductor will be more corrosion resistant all other things being equal than a bare conductor. Insulation also provides chemical as well as electrical insulation. If you can seal the connection to a lug with type 1 room temperature vulcanizing sealant or Scotchcast that is even better.

However, stranded wire does suffer from the problem that corrosive gases, vapors, aerosols, and liquids can flow up between the strands and produce hidden corrosion inside of the insulation. Hence, the invention of Pirelli Strandseal conductor that has a strand blocking compound. Wire strands that are plated with Indium, Nickel, or Tin also are more corrosion resistant - which kind of plating to use depends on what kind of corrosives that are in the environment.

Also, stranded conductors offer more surface are for corrosives to attack than solid wire.

Stranded conductors can also suffer from some of the wire strands NOT conducting electricity particularly when the conductor ages even in a dry allegedly noncorrosive environment.

It is also more likely that solid conductor will be subjected to the #220 silicon carbide abrasive paper elbow grease electrical grease method thus producing a better connection.

I also have some experience with a place that recycles foundry wastes from aluminum foundries. The molding materials liberate ammonia gas when wet which is murder on copper wire even though the concentration is low enough that the air is breathable. The fluxing salts are a mixture of sodium chloride, potassium chloride, and sodium fluoride. The combination of ammmonia, fluxing chlorides, oxygen,m and water will dissolve every useful metal that there is except Indium and Bismuth. In the watewater treatment building of this place stainless steel just simply rots.

I have also worked in a food plant where stainless steel machine screw threads would rust!

For these