Brushless sucks for crawling. I don't know if it will ever work right. You just can't beat the holding power of two brushes being held firm against the comm - its like having a disc brake on the driveline that you can adjust by spring tension, that combined with drag braking in the ESC and the brushed systems just work better. May not always be the case, but it is right now.
I have to disagree here. I have been researching crawlers as I am thinking about buying one this summer. From what I have been reading, the drag brake on a good brushless crawler system, like the Novak Rooster system, is more than adequate to keep a crawler from rolling.
Here is a quote from RCCA magazine in the article about a Wheelie King crawler conversion using the Novak brushless system:
"I couldn't believe how strong the Novak Rooster Crawling Edition speed control's drag brakes are; the truck came to an immediate halt whenever I let off the throttle and returned the trigger to neutral position....The Novak 55 motor has gobs of torque, which gave the truck the ability to pull itself up and over each rock without hesitation."
—George M. Gonzales, RCCA, May 2008 Issue