Both platforms have their unique features, advantages, and disadvantages.
If you are going to add dynamic content on your site using PHP or CGI scripts and want to interface with a MySQL database, then you should choose UNIX for better compatibility with these applications.
However, if you are going to use ASP/Access scripting combinations, ColdFusion, VB scripts or an MS SQL Server database, then choose Windows. However, you will need Windows hosting if you are going to develop in .NET or Visual Basic.
I recommend you to use Windows Shared hosting of AccuWeb Hosting. I am using their service from the last five years.
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