All else being equal, Fire Damage is the same as Health Damage, or any other damage (ignoring Stamina and Mana damage here). What is different is the counter effects.
Some are resistant to Fire, like Dunmer. So, 50 points of Fire Damage to them is not 50 points of health damage. Also, you can take a Fire Resistance Potion and not be affected as much.
Also, something on fire will have more damage received than something this is just blasted.