The main difference between compiled and not is a short hit to turn the
page(s) into IL when they are hit. It is a very small perf bump and only
occurs once per deploy.

The bigger issue is having to deploy all of your source to the server. While
MS states it is safe, I would not personally risk it. Of course, the
compiled bits are not much better if one can compromise the bin folder, so
it is only marginally better. With publish (precompile) you can obfuscate
the assemblies, however.

I see absolutely no reason not to precompile, unless the developer is
writing his code in the ASPX page insstead of in code behind.

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