Sounds like a sweet problem to have. Either way you end up with a cool boat.
I admit to some bias since I own an 18SX but hear me out. The Tornado would of course be faster since it has more sail and is wider and so on. But that extra width means you probably would need a special tilt trailer assuming you can't store it mast up near the launch site. I have never been on a Tornado but have watched videos of them and I can't imagine soloing such a beast. It is not likely that you would be able to right it by yourself.
The 18SX is still a fast boat and can be soloed in lighter winds. I will admit that I have not capsized by myself so I can not comment on whether it can be righted solo. The wings do make the boat a lot more roomy when you want to take the family along. My typical crew and I weigh around 300lbs and we have a blast. When it starts blowing over 20mph consistently we need to be double trapped or we need a third person.
All in all I love my 18SX, but I would sure like to go for a ride on a Tornado!
I hope this helps some and let us know what you decide on.