All three are strong regulators, but compensation, leverage caps, complaint routes and regional scope differ.
FCA, ASIC and CySEC are all high-quality regulators, but there is no simple universal ranking. Look at the entity you contract with and local protection.
FCA often links to FSCS. ASIC focuses on AFSL and retail CFD limits. CySEC operates under EU MiFID II and covers many European platforms.
The same brand may have FCA, ASIC, CySEC and offshore entities. Your protection comes from the entity in the client agreement.