Italian Ab initio or Spanish B SL in IB?Watch
But please don't base your decision completely on which you think will be easier; choose the one you fell intrigued to learn about. Did you enjoy learning Spanish? Or are you done with it and you want to start from scratch? Remember that you spend time studying culture and literature (I do Spanish HL). Does the Italian culture and language intrigue you?
Hope this helps, let me know which one you choose!