Do ATPL
The difficulty of doing the CPL and IR exams exceeds the ATPL in terms of cost and in terms of exams needed to be sat.
Although the content is almost identical the advice would be to do the ATPL -you must sit CPL and IR flight tests and pass within 3 years - otherwis a REPASS is required
The effect is really to make the CPL exams only for those who never want to fly for an airline but may want to instruct
The IR in isolation is for PPL who want that rating
The ATPL is for potential airline pilots
For these reasons the number of peple who sit IR or CPL written exams each year is very low
Its abuot 20 candidates each yera in the UK for the IR wittens - its really not a rating as such for light aircradt its a hoop for the airlines..such a low take up by PPL as to be laughable ..