Differences between JavaScript Remoting and apex:actionFunction component

The component also lets you call controller action methods through JavaScript. However, there are some differences between the two:

Component

• lets you specify reRender targets
• submits the form
• does not require you to write any JavaScript

JavaScript Remoting

• lets you pass parameters
• provides a callback
• requires you to write some JavaScript

In general,  is easier to use and requires less code, while JavaScript Remoting offers more flexibility.

Moreover, JavaScript Remoting helps in reducing View State size and also provides you near real time transaction.