While not a Dynaudio/Harbeth comparison, I did spend quite a bit of time auditioning the Dynaudio line about 3 years ago. While Dynaudios are a very good speaker, I ended up with a pair of Spendors, a British cousin of Harbeth that are similar in character.
I just found the Spendors more lifelike for the type of listening I do. The Dynaudios were just a bit too "sterile" for my tastes.
Since both the Dyns and Harbeths are excellent speakers with good reputations, you'll really need to listen for yourself. Different people are going to come to different conclusions.