What is the difference between using 'devenv' and 'msbuild' in CruiseControl.NET builds?

What is the main difference between using the <devenv> tag and the <msbuild> tag is in CruiseControl.NET?

I understand they call different executables, but sometimes I get different results (as far as pass/fail at compile time), and I would like to know why there is a difference between the two build commands.