Our thoughts will subjective and in most cases limited to only 2 papers (as u attempt only 2 from 4) so hard to compare what would be easier the actual exam somebody took or the one he didnt choose to study and sit.
I recommend selecting paper not on the ‘easiest to pass’ base but your personal interests and career path you would like to follow.
I would never ever sit Tax Paper although it has highest pass rate from optionals.