Does Image stabilization make a difference?

No I would not say the IS is needed for baseball games or really sports in general. To avoid camera shake you need to shoot at least 1/focal length of lens. So if you have a 300mm lens then you need to be shooting at 1/300 of sec or faster preferably 1/500 of second. Since sports games are very fast moving a lot of the time you want to be shooting at higher shutter speeds. 1/250 is a minimum to stop motion, but often times thats not even enough and you are better shooting at closer to 1/1000 to really be assured of sharp pictures. What I am trying to say is, is that at a sports game IS becomes useless because if you are indeed shooting at such a low shutter speed that you need to use IS you wont be using a fast enough shutter speed to stop motion anyways. There are exceptions however, say you are using your lens at 300mm and its dark out so you are pushing the limits and shooting at 1/250 of second to get the most out of the ambient light, in that case IS could be useful. However many sports shooters use monopods which can be fairly cheap. Personally I dont have IS on any of my lenses and dont really ever run into situations where I need it. But then my lenses are all in the f/2.8 to f/1.4 range so that helps a lot. I would personally also spend more money on a better lens without IS then get a cheaper lens with IS.