I voted Road-runner.
If I recall correctly speedy ran fast to get food, his need for speed was to eliminate hunger.
Road-runner ran fast to avoid being eaten, his need for speed was to eliminate certain doom.
Since speedy would most likely be running to get food (aka road-runner) and road-runner would most likely be running to avoid the eater (aka speedy) this arrangement requires road-runner to be in front of speedy...and hence road-runner would cross the finish line first.
So was my logic at least.