ok im going to lay off the scorps vs. banshees options and tell this guy what he wants to hear...
if you have guardians and a seer council then your well of as some first points but your going to want some long range shooters, i would recommend both reapers and rangers, you can swap depending on if the troops can be pinned or not. then youll need something to absorb firepower, i would personally choose either a wraithlord, wraithguard, or some warpspiders. the wraiths are obvious but let me tell you why warps, if you can move as fast a warps can you can give you opponent a target quick wich will make him not think to utilize mobility, once you have the cornering force of mobility take some vipers or a falcon with fire dragons and take out his armored vehicles and then mob up with loads and loads of shreiken fire...