I like Speed Circuit because it's more a simulation of driving a car. Your speed is scaled and chosen by you. It's also a guessing game between you and the other drivers. This is unlike Formula D where dice determine your movement.
A friend owns Speed Circuit. We've been meaning to try it sometime.
The dice in Formula D do control the distance you move, but the non-standard distribution of numbers on those dice gives each player a fair amount of control over their car. Not perfect control, but a game with perfect control and sequential movement would be pretty boring. I never feel that Formula D unfairly penalizes me with randomness. If I make a mistake and crash out in Formula D, it was my fault, not the dice. Also, if I don't win, it usually means I wasn't aggressive enough or didn't take enough chances. The player that pushes their luck the most without getting burned is usually the winner. That works for me.
If you do play, get a hold of the WBC rules variant. It extends the game a lot.
http://www.lucidphoenix.com/sc/rules/rulesnew.asp?wbc=y But first play it with the basic rules or you might be overwhelmed.