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?

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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.