While the Enclave makes their armor look cool and may be better than other armors, most people aren't gonna have access to Enclave equipment, so general use the Brotherhood win since they usually prioritize protection in the more common T suits.
I'd say the Enclave because the Brotherhood still uses pre-war power armor, while the Enclave spent decades developing the prototype X-01 armor into their Advanced Power Armor.
Enclave PA gives some of the best protection from everything in game and is just better than brotherhood, mainly because the brotherhood's armor is all prewar