That's like comparing Christy Brinkley to my grandmother (she was hot in her day) .OK, so here are my impressions as a novice autocrosser... I have the 245s in the rear, btw.
The RE-01Rs felt a little MORE sticky to me than the worn and two-year-old A048s, and felt like they break loose just a little less linearly, for what that's worth. I could really get the A048s to slide nicely, but the RE-01Rs were a little less linear at the limit, but still predictable. Maybe since the RE-01Rs were stickier? Again, keep in mind this is all relative to worn A048s with 6k miles on them.
So for a novice autocrosser, I'd say you do not give up anything with the RE-01Rs, as compared to worn A048s. I really did not notice any lack of turn in sharpness out on the course, either, despite noticing it around town when I look for it.
In summary, if you're looking for a much more quiet ride, a little more comfortable ride, wouldn't mind longer tire life (from what I hear), and you can get over the psychological difference of less crisp turn-in, these tires are a strong choice for you. That is, the turn-in out on the open road is really the only negative part of the RE-01Rs I have noticed, and even then, I didn't notice it one bit while autocrossing. I notice it mainly when I oscillate the wheel back and forth quickly, which I just don't think happens all that often while actually autocrossing.