This question is not necessarily coherent, since subjective reason is a non-sequitur. If you mean, “When is intuition more useful than reason?” then that is a question currently addressed by Kahneman and Haidt. Intuition is very powerful, but not logical or observable. Reason is very weak, but observable. And they inform one another. However, any concept of truth is determined by reason. Any concept of preference by intuition. And we lie to ourselves whenever possible in an effort to conflate the two. https://www.quora.com/How-can-one-determine-when-subjective-reasoning-might-be-preferable-to-objective-reason