I am currently working on a project that is written in PHP...  Very poorly.  I have to do a complete re-write.  I can code in either language, so I am trying to determine if I should convert to .Net or not.

Is one really any more scalable than the other? 

Is there a noticeable difference in speed between the compiled code and the interpreted code?

Is there a list of large, high-volume, commercial web sites (other than MS, of course) that run on .NET?

Thanks.

J

 >Is there a noticeable difference in speed between the compiled code and the interpreted code?

Once the compiled code has been JIT'd )occurs on forst load), compiled code runs faster.

For a list of companies see http://www.asp.net/get-started/

It's unlikely that users will notice much of a difference, so long as the hardware is configured corectly to cope with whatever your traffic expectations are.  The largest delay in rendering a page is network related, rather that server-side processing of logic. The main benefit of ASP.NET is not speed of execution - it's speed of development.  One of the benefits of keeping with php is that you won't have to wait for search engines to re-index the new file names.