First of all, this is a topic about pictures of moving objects
Second, ISO isn't realted to speed. The shutter has a speed (the it stays open and let light in), ISO is more like sensibility to that light, but raising ISO, although you can get "better" pics with scarce light, you lower the quality
IMO in your two pics it is the other way around: the second was with ISO set lower that the first one because usually the higher the ISO, the mor ethe grain in the pic.
Anyway, for that kind of picture you shouldn't change the ISO.. since you could use a tripod, you just set the shutter speed to an higher value.
I do the same when I have my tripod (like in the pics for the Ferrari auction): slow shutter (1 sec) and deep field of focus (F8.0).. ISO is to be raised when you are really desperate for more light