frankleeceo - 6:00 pm on Oct 17, 2013 (gmt 0)
The rule is that you cannot modify the codes so that they look and feel different, with the intention to trick visitors into unintentional or invalid clicks.
Leaving out that portion of the async code improves the call as it won't be duplicated if you have more than 1 unit on the page.
You can always leave both codes 100% unmodified but then it's at the cost of your loading speed by a fraction.
Another situation where you can modify the code is for "responsive" purposes.