implementing ASP.NET-ajax download - which way is better?

I want to implement an ASP.NET-ajax downloader, and got across two alternatives for doing so.

http://encosia.com开发者_JS百科/ajax-file-downloads-and-iframes/ with the use of IFRAMEs and http://archive.msdn.microsoft.com/AjaxFileDownload with the use of MS-Ajax Library.

My question is, which of the two ways is better, and why? What should I consider when implementing this?

Use the iframe approach and avoid Microsoft AJAX JavaScript library because it's considered obsolete in favor of jQuery.

Do so with jQuery and AJAX, and the so-called iframe.