I work at a Microsoft shop doing mainly web development.

We had a client who asked us to review (improve) the data model for his web app, but said that he wants to develop his app in PHP (he knows "a guy" who can do it).

When I asked him why he wants to go with PHP, he gave me the standard set of arguments from the 90's:


Microsoft is evil, and PHP is free
Writing an ASP.NET app is more expensive (software-wise)
Why would Facebook use PHP if it was a bad idea? [classic]


He had a few more comments about the costs associated with going .NET.

The truth is that "Microsoft is expensive" does not hold water any longer, with their "Express" suite, you can develop an ASP.NET app without paying anything for software.

When it comes to hosting, you can save a few bucks with PHP over .NET, but that's a small fraction of the projected development costs (we quoted 10-15k).

Going back to my question, what arguments would I give to a client in favor of ASP.NET over PHP? [please provide sources for quantitative claims]

Just Tell him the truth.. You are not a PHP shop. (That's reason enough why YOU can't do it in PHP)

This is the price you are quoting for .Net. If he can beat that elsewhere, so be it.

It's a horrible sales tactic to knock down your competition based on the platform used. (Even if it has a lot of weight in the clients mind) 

Sell yourself, Sell your Strengths, admit where you lack expertise. You will win the job on your merits.

"We can build great Websites, look at our portfolio, Look at our track
record, check our references. We can do what you asking and we can do
it at a fair & competitive price, But we can't do it in PHP."
