I have owned both (Harbeth SLH-5, Monitor 30 and HL-PES2 and the JMR Duet). I would say...
Harbeth: clarity, natural tonality, refined, polite and somewhat restrained
JMR: even greater clarity, less polite, more exciting, a closer-in perspective
Harbeth: clarity, natural tonality, refined, polite and somewhat restrained
JMR: even greater clarity, less polite, more exciting, a closer-in perspective