well MoK princes can't take psychic powers and are the worst setup except an unwinged, unmarked prince.
So if you want a CC prince any of the marks are useful in someway, slaneesh generaly strikes first, nurgle is good vs low str hits and tzeentch good vs armour ignoring hits.
However 1 thing to note 5 attacks in close combat i've often found is just not enough even if you have warptime, which is why you will generaly see princes run in pairs and they will assault together.
I'll quickly list some good prince setups i've had sucess with and bear in mind all have wings:
Warptime - Cheap and perfect for low point games
MoN & Warptime - this guy is awesome against basic troops but you really have to watch out for anything Str8 that ignores armour.
MoT, Warptime & Wind of Chaos - This guy can take down a full 10man SM squad solo
MoT, Warptime & Bolt of Change - Not as effective at taking out full squads but the S8 AP1 shot can pop a transport and let you assault whatever was inside, something to consider.
MoS & Lash of Submission - Do i need to say more? i mean when i run a dual lash list 1 squad is pulled into my army shot and then assaulted if it's still standing. I wouldn't take warptime simply because you can take lash and just destroy units easier buy pulling them in and using your entire army to destroy them.
As for your friends idea the problem is that when units DS they can't assault so the termies are going to get shot to hell before they can do anything and trust me a 5+ isn't going to save them. Hell i'd love a set of melee termies to drop right infront of my oblits, it would honestly make my day, i would suggest taking some combi weapons and always get a chainfist and a heavy flamer, if he uses the icon you can drop them next to the ranged squad and shoot the crap out of them first and reduce the amount of return fire.
Oh ye the lord, um i hate lords, princes are much more efficient but if thats what he wants... infact screw it just tell him to get kharn, charge him into a unit solo (avoid anything S8+) and watch his beautiful work, i've seen him take down a trygon solo he's just that badass.
Last edited by OpTi; 08-23-10 at 08:40 PM.