I have been going through the same process, releasing the 12.2.5 instance to the users, and the users have been finding many issues that we have to apply patches for which are included in 12.2.6 and 12.2.7. If you go with the most recent release (only been out a few weeks), there is always a risk of hitting an issue in 12.2.7 which is not in 12.2.5, but there is also a higher probability of having to patch for issues fixed in 12.2.7 which are not included in 12.2.5. In general, Oracle fixes more bugs in major releases like 12.2.6 or 12.2.7 than they break, but you still need to test the critical functionality that you have to have working for your business.
What are the main advantages if we choose to go with R12.2.7 instead of R12.2.5, please be specific?
We had tested earlier with R12.2.5 and found few patches that we installed. We can test again with R12.2.7 once decided.