Anyone have a good side by side difference between managed and nonmanaged bundles?

The only difference I know is that with Managed Bundles you can push updates from the source account. Also if you try to pull the update of a Managed bundle, NS wont allow you

yes that is the main difference. and pretty much the only difference.

I did not see any option to create Managed bundle. How can we create one?

There should be a check box "Managed Bundle" when you are creating bundles. This is usually disabled, I think you need to contact support so that you can have the field enabled in your account.