A similar article can be found here.
http://www.thefootballeducator.com/m...ation-process/
According to it (by their definition), the success rate of a fifth is 3.8%, while the success rate of a sixth is 2.5%.
3 sixths will accumulate to 7.5%
2 fifths will accumulate to 7.6%
3 sixths would definitely give you a higher success rate (7.5%) as compared to one fifth (3.8%).