If you think that 1000calories from white granulated sugar and 1000calories from sweet potato or rice are the same and they are going to have the same effect on your muscles ,there is nothing to argue about.
Ok micro-nutrients aside , where is the difference ? The human body breaks all carbs down to glucose which is then stored in your muscles and liver with the help of insulin.
The total amount of insulin needed to store the glucose is the same in both cases. The sugar will create a much higher insulin peak and blood sugar levels will drop faster of course. This can cause cravings and make you feel tired. Note that the amount of energy is the same though .. feeling tired does not automatically mean having less energy (talking about energy in a physical way)
I'm not saying that it's the best way to do it , all I'm saying is that it won't matter in terms of fat-loss or strength/muscle-wise. It might make it harder for you to stick to your diet .. but it can also make it easier. Instead of just eating plain rice you can just try eating fruits for example (which to me taste a lot better) and spread your meals out a bit. Will also make your blood sugar levels more stable.
What I also noticed is that if i get most of my carbs from simple sugars I tend to look "fuller" in comparison to the same amount of complex carbs.
My theory is that a high insulin peak will force your body to store a lot of the blood sugar in your muscles instead of just using your liver as storage.
Usually sugar is first stored in your liver and then in your muscles .. which is why it can be quite hard to carb-load in one day if you were completely depleted before. Takes a while..