Complex sentence: Actually, Borges claimed that the entire Florida-Boedo rivalry was a pointless imitation of European fashions and that, if forced to choose sides, he would have picked "Floredo".
Split into simpler sentences: Actually, Borges claimed that the entire rivalry theme was an imitation of European fashions and thus "pointless". He said informally that, if he were forced to choose sides, he would have probably picked "Floredo".