I think it's fair to say that a consensus has already been reached. From CAP 804, Section 1, Part E:
2 Required Information
2.1 Part-FCL.050 and the ANO require a flight crew member to keep a personal flying log in which at least the following particulars are recorded:
....
2.1.2 Operational conditions, namely if the operation takes place at night, or is conducted under instrument flight rules.
The ANO requirement to record 'instrument flying' is also retained, although there is no definition of what constitutes 'instrument flying'. This, of course, takes account of the fact that, from 17 Sep, both the ANO and Part-FCL are law in the UK although, in the case of conflict, Part-FCL takes precedence.
I suppose that it may be said, therefore, that the 'small benefit' is that one keeps within the law.