Corythia

From my experience, both Fire/Dark and Plant/Nature are both very resilient and can solo easily. Plant/Nature takes a little longer to get rolling. If you want something powerful with a self heal either or both are very good and very fun.

I have Ice, and Frost Breath deals a LOT more damage then either fireball or the earth aoe. The rain power in addition makes Ice much better if you are just looking for dps. The ice armor is great, but it really messes with your costume. Hibernate is great since you can get everything rolling then hibernate if you are taking too much heat. Honestly with Plant/Storm Ice also has the best synergy since you are starting with a big cone attack, then debuffs, I tend to stay where I started till the minions are cleared and I move in to concentrate on bosses. That makes the frost breath cone and the rain easy to use. Plant/Storm was my first 50 on Homecoming, and I still play her a LOT. Ice is the way to go.

I think Plant, Fire, Illusion in that order. If you aren't worried about damage output till the 40s, Earth with the earth epic does a surprising amount of damage with an amazing amount of control.

I have to say Earth/Storm is my favorite as well. I am enjoying Earth/TA, Fire/Dark, and Plant/Storm as well.. I have a Grav/Time controller that was ok at lower levels, but I find it has a really tough time against groups that spread out at all. I thought Ice/Storm would be strong, but anything that resists cold will wreck it, it doesn't have a second string to it's bow. I think that's it for now. I want to try Electric/something, but I'm having trouble deciding on the secondary.

I have an Ice/Storm controller, and compared to other /Storm combo's it feels weak on both control and damage. If you don't mind waiting till your 40's to solo, I would recommend Earth/Storm. For something that solo's easily earlier, Plant/Storm and Illusion/Storm are both powerful by level 20. Storm is my favorite secondary for controller, though it does require a lot of practice. A poorly played storm character can slow a party down, or even cause wipes. You have to be careful of when and where you place your tornado and lightning storms. With Illusion, a knock back to knock down IO in tornado will be almost required.