As you know, the Varia Suit adds heat protection and 50% damage reduction. The Gravity Suit however, overrides and negates the Varia Suit's abilities. It decreases damage by 75%, adds water and lava mobility and heat protection. Go to Crateria with just the Gravity Suit on and run into a geemer. It'll do 1 damage. Go to Norfair and you're still protected from heat. I discovered that completely by accident.
Yup, but i believe it only gives you 50% protection instead of 75 without varia suit on.
The Gravity Suit gives 75% protection. It cancels the Varia Suit's 50%, keeps heat protection while adding lava invincibility and thick environment mobility. I tested it myself.