a. Using access-list command and b. Using ip access-list. The difference lies between them will make you think twice before you choose one of them.
Here is is an simple example to configure a standard access list using method a.:
Look at what you got after you delete one of the items in the access list created by method a.:
The standard access list is gone even you only delete one of multiple access list entries!
Now look at the example below to see how to configure a standard access list using method b.:
Now look at what you got after you delete one of the items in the access list created by method b.:
This is great and provides more flexibility in designing and managing access lists.
Besides, using ip access-list also gives you the option to design named access list.