LINQ is one of the greatest improvements to .NET since generics and it saves me tons of time, and lines of code. However, the fluent syntax seems to come much more natural
I have just set up our company's standards and we enforce the use of the Extension methods. I think it's a good idea to choose one over the other and don't mix them up in code. Extension methods read more like the other code.
The comprehension syntax does not have all operators and using parentheses around the query and add extension methods after all just begs me for using extension methods from the start.
But for the most part it is just personal preference with a few exceptions.