The main advantage of using Shopify Theme 2.0 Widget Blocks is that it allows for consistent positioning of your bundles across any page in your store.
This makes it easy to keep bundles in the same place without having to manually make changes or reposition them. Additionally, bundles injected using the Shopify 2.0 placeholder widget will be displayed in order of priority, so you can control which bundle is displayed when multiple offers are selected for the same page.
For more information on this as well as other positioning methods check out the following articles: How to inject a bundle offer with the Shopify 2.0 app blocks, How to use the element selector bundle injection and How to custom embed a bundle offer.