Have not heard the P5 or the P7 (or the MS500), so I cannot comment there.
You might want to float your inquiry on the dedicated Mikros 90 thread and ask the other folks here who are better qualified than I: http://www.head-fi.org/t/633514/martin-logan-mikros-90-on-ear-headphones
Be forewarned: opinions are dichotomous/controversial. But most of us who have owned longterm, enjoyed and subsequently endorsed the Mikros 90 have come to the consensus that (1) criticality of proper placement and/or (2) sub-par equipment and/or environmental conditions (in that order) have probably disuaded many who perhaps would have otherwise come to appreciate the MLs. Individual listening preferences divide the opinions as well. Unfortunately, many thread-subscribers may have reached their "guilty" verdict second- or even thirdhand, based on hearsay, without actually having heard the Mikros 90 themselves under sufficient conditions.
I have had relatively little exposure to supra-aurals and IEMs, so my reaction to and comparative assessment of the Mikros 90 are based primarily on a personal history of mid-to-upper mid-Fi circum-aural headphones (e.g. HifiMAN HE-500/5LE/6, AKG K701, Beyerdynamic DT880/600ohm & Tesla T1, Sennheiser HD-600/650, Ultrasone PRO750/2500/2900).
To my ears, the Mikros 90 occupy the top tier among all the headphones I have heard/owned to date. That is not tantamount to saying that they are "perfect" or the "be-all-and-end-all", but they do seem to bring together into one tidy and affordable package many of the listenability attributes that I, personally, consider critical: balance, clarity, frequency extension, high levels of detail/resolution, coherence, tonality, timbre, dynamics and sense of spatiality; but--most importantly--given all the Mikros 90's technical agility, these headphones ultimately produce a satisfyingly musical outcome.
Too, I will posit that the Mikros 90 have more of a cerebral than visceral presentation, and have been catalogued by some reviewers as "gentlemanly" or "refined". But these descriptors should not be taken to mean that the headphones are therefore uninvolving--far be it! With the MLs, the listener takes a more active than passive role; these headphones favor one who wants to to hear the details of deep bass and not simply feel some bass. While they lack the midbass hump/thick spot of many popular headphones, I have experienced clean, extended bass from the Mikros 90 that seemed to shake the ground below me.
. . . O.K., O.K. (they've just administered me the smelling salts), you must have gotten the impression by now that I am a shameless proponent of the Martin Logan Mikros 90. Take this query to the dedicated Mikros 90 thread and get more feedback there.
Yours Truly (while gradually coming out of a hyperventilated state),
Edited by pataburd - 1/14/14 at 6:27am