Siren vs Fenghuang: who would win?

Siren favored — Slight edge (~55%)

Siren · God of War · Base

Tier

8-C

Attack Potency

Building Level

Speed

Sub-Relativistic+

Durability

Building Level

Fenghuang · Kung Fu Panda · Base

Tier

8-C, up to HIGH 8-C

Attack Potency

Building Level, up to Large Building Level

Speed

Supersonic+

Durability

Building Level, up to Large Building Level

A heuristic estimate from normalized VS Battles Wiki stats: tier, attack potency, speed and durability.