✔ 最佳答案
It depends on which overseas country(ies) that your friend chooses.
For all Commonwealth countries except Canada (U.K., Australia, etc.), IELTS is preferred.
For the rest of countries, TOEFL is preferred.
Please note - due to long history of TOEFL (and the easy scheduling), there are more institutions accepting TOEFL rather than IELTS.
So my recommendation is unless your friend has decided for Commonwealth countries only, always take TOEFL.
A quick note - as he/she has graduated with a Bachelor's Degree, it does not matter what your friend's HKCEE/HKALE results are. A language test will be required regardless (even in Hong Kong).