The only reason to do a NG+ run in ME3 is to at least get the Gunsmith Trophy/Achievement, at least with the first game you can tell me it's because we can have access to more dialog options using our accumulated Charm/Intimidate points.
It's weird that you don't get the credits transfered as doing a NG+ in ME3 is the only way to have credits transfered over, unlike ME1 to ME2 where now Bioware nerfed the amount of credits we get. I know of a bug that happens and turns your costume Shepard into the generic soldier on level 1 without credits and no skill points (I fixed it easily by loading the closest safe) so there is that.
