Probably any grease will work that will stand up to underhood temperatures. I've used wheel bearing grease for decades on battery terminals and it's worked fine.

Lithium grease is a lubricant for used in hinges, bearings, joints etc. It's job is to reduce friction and metal wear. It has a high resistance to pressure. It is a mixture of oil and metal salt thickeners. Since it contains petroleum distillates, it can attack some polymers.

Dieletric grease is used for sealing electrical connectors (among other things) from moisture and air to prevent corrosion. The silicone oil is water resistant and neutral. It won't attack rubbers and plastics, which is why it's used in connectors with rubber water seals. Dielectric means it has excellent insulating properties, and won't conduct in the presence of a high voltage electric field (such as in your ignition system). It is also more stable at high temperatures. Also, because silicone grease is neutral, it gets used a lot in food industry, as it is safe for humans.

These different properties make each one suitable for different applications. I find them both very useful, and keep both in the home. I also apply dielectric grease to my door seals to keep the rubber supple and prevent it from drying out and sticking in the winter. Hope that helps.