When I first got the game, I had seen comments from people saying they thought it was far easier with ABS, so I had kept it on for several weeks, and after finally feeling like I'd gotten a solid handle of the gameplay I kept noticing that most top times (as the OP pointed out) had no ABS... so I tried it, and found that if you're not mashing the brakes, you definitely have a much more precise and controlled braking slowdown, unlike ABS which tends to lockup far easier and on a standard controller can hardly be prevented.
ABS off simply requires a bit of finesse, but definitely provides better results in terms of lap times. ABS is just more forgiving when you make mistakes in late brake situations.