As anyone who follows my posts should glean that when I eat grains I aim exclusively for the full wholegrain since these are what I consider good carbs.
Refined carbs such as white bread (and flour), I consider a processed food and so avoid like the plague. I was thus interested in a youtuber called Footsoldier's recent vlog entitled UK WHOLEGRAIN BREAD CONSPIRACY which tries to find good wholemeal bread in major UK supermarkets. It shows how even expensive breads such as organic or spelt are often based on white flour. (It may also be useful to vegans since it highlights some breads that contain milk and eggs.)
What is my problem with white/refined flour & bread? It has much of the nutritional value extracted or destroyed. You can see this because, by law, they have to add back some useful nutrients such as niacin, and thus the flour is often called fortified flour. A key point is just because some destroyed ingredients are added back does not mean that you end up with the original product. Only those ingredients that have been legally identified as causing harm to health are in the fortification list.
Health-wise I think white flour raises blood sugar levels and can increase likelihood of diabetes. This is especially true when presented in that most desirable of all bread products, the croissant because of the inherent salt, sugar and fats.