異步或同步加載更好？

Question

發現於JavaScript SDK http://developers.facebook.com/docs/reference/javascript/

"... 
    Asynchronous Loading 
    -------------------------------- 
    This code loads the SDK asynchronously so it does not block loading other 
elements of your page. This is particularly important to **ensure fast page 
loads for users and SEO robots**. 

    Synchronous Loading 
    -------------------------------- 
    It is possible to load the SDK synchronously which may be useful for 
debugging, but this method is not recommended for typical use. Synchronous 
operations will block the web page, resulting in worse performance and a 
slower user experience. This **may also negatively impact SEO due to the 
increased slowness perceived by robots and crawler**s. ..." 

所以，這些陳述是正確的？

Answer 1

兩者都是。

對於調試Sync是好的。

對於生產代碼異步更好。