as per Outpost, a larger rear bar will offset much of what you lose with no front bar plus you have the added benefit of much improved drag strip traction (air bags usually not necessary and car twists much less)
I did some experimenting with the front bar on/off and 90/10 shocks on/off.........with stock shocks (KYB) and the front bar, my 60' times slowed by 1-1.5 tenths and try as I might, I couldn't come close to equaling the no bar 90/10 set up. Results may vary........