Yay for controllers!
I have to say, I'm a bit partial to Stormies. Einen is a Storm Defender.
But as for controllers, I personally like Ice as the primary to Storm. They go together wonderfully. They're a bit of an End hog together, but the benefits are worth it. You'll end up having 2 ice slick powers which keeps most enemies unable to attack, which are very nice. The slow powers all work well together, and once you get above 20 or so, you should pretty much be able to control a group for as long s necessary. Ice/Storm isn't the highest damage output, but, when enemies can attack at all, your slows should at least double their recharge. If you are planning to use Ice Slick/Freezing Rain, one thing to note is that AoE immobilizes kind of ruin the point; as they give knockback prot the enemies can still attack. Ice/Storm works best on a team, in my opinion anyway :P, So it could work out well for you running with your friend.
I've played a number of Controllers, and I've found Ice/Storm to be the best for keeping groups at bay, however, it's definately not the best for dealing damage.
A good friend of mine played an Illusion/Storm. It seemed like alot of fun, and it was definitely a good build; Illusion is a good set in general. In fact, controllers are a good AT in general :P Illusion will give you better damage output, I think, so that might be good for running with a new player as well...
But again, when running storm, I'd recommend not going with AoE immobilizes. And I hope you have fun with your storm troller!
~ @Einen
Playing Storm is easy. Turn on Hurricane, set a Tanker on your team to auto-follow, and go make lunch.