After running a few tests, it looks like having a type advantage increases damage by roughly 30%, which having a type disadvantage decreases damage dealt by about 15%.
To test this I took 3 spirits with equal attack values and made teams out of them:
- Kammy Koopa, Atk 500, Attack Type
- Porygon, Atk 500, Shield Type
- Staryu, Atk 500, Grab Type
The Porygon also has 500 Def and will be used as the target for these tests, hoping that having Atk and Def even out helps us focus on just the type advantage results.
Then I went into training mode and tested by using fully charged side smash attacks with Marth.
When testing with the same times (Shield vs Shield), I dealt 20.1% damage
When testing with a type advantage (Grab vs Shield), I dealt 26.2% damage
When testing with a type disadvantage (Attack vs Shield), I dealt 17.1% damage
If you divide the standard results with the advantage results (26.2/20.1) you get 1.303. So a type advantage grants roughly 30% extra damage output.
Dividing these standard results with the disadvantage results (17.1/20.1) you get 0.850. A type disadvantage thus reduces damage output by roughly 15%.
For a second test, I repeated the general steps from above but this time with Atk and Def values around 1000 to see if the results remain consistent.
Here I chose Urbosa (Attack, 1011 Atk), Blooper (Shield, 1003 Atk), Solidus Snake (Grab, 994 Atk), and Houndoom (Attack, 997 Def).
(The Atk values aren't exact with this test, but a quick test with two spirits with a 16 point difference in Atk values dealt the same damage in this test, so I'm assuming here that the differences are minor enough to not largely effect the results.)
After repeating the test, I got:
- No Advantage: 19.1%
- Advantage: 24.8%
- Disadvantage: 16.2%
The previous calculation here yields 1.298 (vs the previous 1.303) and 0.848 (vs the previous 0.850).
To be extra thorough, I tried this test one last time but with the 1000 Atk spirits vs the 500 Def Porygon spirit.
- No Advantage: 23.5%
- Advantage: 30.5%
- Disadvantage: 19.9%
This gives 1.297 and 0.846, which stays in line with the original 30% and 15% estimates.