Would be best to consult the reviews in this forum for those, but I'll give a short roundup
IE8 - mid bass heavy, huge soundstage and very fun sound signature, shallow insertion so very tip dependent, might not isolate as well as the rest. Upgradable cables are great!
W3 - I have personally not heard these but they are said to be V-curved so very emphasized bass and treble. I cannot comment further though but since I have the UM3x, I am thinking these would be the Pop/Rap/Hiphop versions of these
MTPG - These are probably the best candidates for rap with the huge but still very controlled bass (probably the most out of these 4) and it has the right amount of detail for the vocals. Not as detailed as the MTPC but for solely rap and hip hop it will come down to this and the IE8.
MTPC - The best all rounder out of the 4, right amounts of quality bass although probably less than the other 3, not bloated and controlled, detailed and is the best all rounder out of these. Great mids which complement the bass well and smooth and non fatiguing treble. If you listen to other genres other than rap then these would be the best imo as they perform well with anything you throw at it.