Does Apache with MySql will use less system resources (RAM, CPU utilization) if we develop a web application instead of IIS with Sql Server?
My friend told that MYSQL consume very less when compared to SQL Server.
I have both PHP and ASP.NET skills. Which one will be preferable to develop application?
This will more depend on what you're doing. My experience is that ASP.NET runs circles around PHP when it comes to speed - though most of the times it doesn't matter as you're spending most time doing IO or waiting for the DB:
As for resources consumed, MySQL by default uses very little, if you really want more speed you'll have to tune it - which among other things means tune it to use more resources - RAM in particular. SQL Server is a more complex and feature rich database compared to MySQL - and by default it'll use more resources compared to MySQL, which you can tune down if you so wish.