All types of oatmeal are good for you as they are a good source of fibre. The only difference you will notice is in the size of the flake and the texture of the cereal itself. The important part though is the Glycemic Index of oatmeal. What this means is how quickly a food is likely to raise your blood sugar level. This is something which is very important to know if you are diabetic. Oatmeal has a glycemic index of around 61 which means it acts very slowly at raising your blood sugar levels. In comparison, Corn Flakes has a value of 77 [Note: Both of these values may vary due to how they are initially calculated but are provided here in comparison to glucose which has a value of 100]. Larger flaked oatmeal will have a lower GI compared to the smaller rolled oats. I believe Scott's Porridge Oats are a very small flaked oat but they are 'oatmeal'.
If you are working out, it is advisable to eat low GI foods prior to exercising so that your blood sugar levels will not fluctuate and cause a decrease in your performance and endurance.
Hope this helps you out.