The only main difference in 32 vs 64 bits viewers is reliability, 64bit viewers on a 64bit OS crash less. They are built from the exact same code, have the same features, and should run about the same speed. Intel stopped supporting some graphics when they reached end of life, which means no updated drivers or drivers for newer OS versions, ever. Time to retire that box.
https://community.secondlife.com/forums/topic/446595-firestorm-64bit/