Using Dethrone with 50% Attribute, 40% Crit Chance, 5000 PATK weapon, on a 1000 DEF enemy:
300 STR: 30.95*6900*log10((5750/(1000+1))^0.9+1)
= 163399 Average Damage
150 STR + 150 DEX: 30.95*6750*log10((5375/(1000+1))^0.9+1)
= 155310 Average Damage
300 DEX: 30.95*6600*log10((5000/(1000+1))^0.9+1)
= 147155 Average Damage
Keep in mind that these circumstances will chance based on equipment, gems, accessories, ATKSPD, and much more. One of the most important factors that influences damage is Skill Factor. Consider a full rotation of high level attributed skills, STR will yield higher results unless you have an impossible 1500 CRATE or so. This information is all readily available, use it for your own circumstance.
My Char Info Without Invested Stats:
PATK: 4954
CATK: 353 (5 Ella)
444 CRATE with Finestra = 29%
450 Elemental Property Damage
19071% Total Rotational Skill Factor
60± Hits
367 Invested STR Total 420 STR:
+914 PATK
Gung Ho = (1.72*(420^0.8)+38)*1.5
= 381 PATK
Concentrate = (420+2*70+18.5)*1.5
= 867 Additional Damage
Damage:
6249 PATK
353 CATK
1317 Additional Damage
190.71*7257*log10((6249/(1000+1))^0.9+1)+(1317*60)
= 1175400 Average Damage
With Serpentine and Spear Lunge:
2.0*190.71*7257*log10((6249/(1000+1))^0.9+1)+(1317*60)
= 2271950 Average Damage
184 STR + 183 DEX Invested 237 STR 253 DEX Total:
+589 PATK
+1262 CATK
Gung Ho = (1.72*(237^0.8)+38)*1.5
= 261 PATK
Concentrate = (237+2*253+18.5)*1.5
= 1142 Additional Damage
Damage:
5804 PATK
1615 CATK
1592 Additional Damage
190.71*7114*log10((5804/(1000+1))^0.9+1)+(1592*60)
= 1137700 Average Damage
With Spear Lunge and Serpentine:
2.0*190.71*7114*log10((5804/(1000+1))^0.9+1)+(1592*60)
= 2179890 Average Damage
About 40000 Damage difference per rotation with up to 100000 with debuffs. STR is the clear winner, and that compounds quickly. In certain cases having Mid DEX investment can be beneficial depending on playstyle and exact build, but for most builds, in most cases, STR will just do more damage. Glass Moles will further increase the gap too. This is the specific case for my build and my gear though.