>I can't tell you exactly as I haven't done Silverlight, but LinqToSql is not a prefered method. MS wants you to use Entity Framework.
>
>>I created a Silverlight project. Why is there no LinqToSql in the Add New Item dialog?

I read yesterday a slightly different opinion (unfortunately, in Russian) here Denis Reznik explains what may be better to use

The last blog in his post is graphical comparison results (in English).