Kevin,
I was fully prepared to buy the twighlight blue; sleek and elegant, it was definitely my color of choice. My wife, on the other hand liked the Electric Blue.
Sooooo... as a proud owner of an Electric Blue Sport I can give you a few insights.
[insert your own punchline here.]
Like you, my initial concern was that it would be over the top and look a bit like a cartoon car. With the tan interior, however, it is nicely softened yet still vibrant. The other interesting thing is how the Electric Blue looks with the exterior carbon fiber package. I really like the CF and think it brings a great deal of visual interest to the car. I recently saw a Twighlight/CF car, though, and I was surprised that the darker blue almost made the carbon fiber disappear. In fact, I didn't realize it even had CF until I was literally standing next to the car. The CF on the electric blue, on the other hand, is very noticeable but it also balances out the paint color. The blue takes on a more elegant look and really pops without looking cartoony.
I've attached some pics so please judge for yourself, but if you like the Carbon Fiber I'd definitely go Electric Blue. If not, choose whatever moves you.