In comparing the same oils with the same trade names, there won't be any difference in the product, only in the packaging.
There are some products from major blenders that are available in bulk but not in retail sized containers, unless you consider a 55 gallon drum to be of retail size.
If you compare pricing for bulk oil quantities with the typical on sale somewhere price of retail packaged oil, you'll find that bulk isn't any cheaper.
It's more a matter of not having to open and then dispose of a bunch of quarts or jugs every day in a busy shop.
Also, it's a lot harder to convert bulk oil to personal use than it is oil in jugs or quarts, for those shops that have employees who might be tempted to be dishonest.