Well, from a true road race tracking perspective I couldn't be sure. From an autocross perspective, the spring rates are so soft that the simple extra roll resistance outweighs anything negative about a stiff front bar. The car just plain pushes, so there's just no such thing as this car not pushing. If anything it's a good learning tool since with that much bar, you have to be even smoother with your inputs. Slaloms are slaloms, but with every other manuever, you NEED to engage the tires smoothly. With the street tires you notice and feel it, but then with R-comps you don't since the stickiness of the tires allow you to go past the optimal input without much feedback, but all that means is you're slower without knowing why.
so unneccesary diatribe aside...I'd say a stiff front bar is 100% win in autocross. Tracking doesn't have as much transition, so body roll isn't as much a killer as in autocross