BEx Analyzer Vs Web Reporting

Hi,

We are noticing Queries run 2x time fatsre on Web/Portal when compared to executing on BEx Analyzer (Excel).

Ex: A COPA BI query when executed on Web/Portal takes 1 Min (60 Sec) to get the results,Same query with same selection variables when executed on BEx Analyzer is taking around 2 Mins (120Sec) to render the results.

I tested around 10 different reports and conclusion is Queries run 2x time fatsre on Web/Portal when compared to executing on BEx Analyzer (Excel).

Is there any technical reasoning behind this,I am investigating on my manager behalf to submit proposal to move BI reporting to SAP.

Any supporting documents (Blogs or SAP Notes) regarding this is  will be greatly helpful.

Thanks in advance