I am not sure that what you log is sensibly the choice of the individual pilot. He/she ought to log what the regulatory regime he flies under says he/she ought to log.
JAR has got itself rather confused over IFR and IMC wrt logging time. In the UK it is further confused because UK rules require almost ALL night flying to be under IFR rules even when it is visual contact flying (i.e. VMC). For night visual contact flying in the UK you do not need an IR or an IFR equipped helicopter, even thought the flight has to be made under IFR rules.