From the fantastic book, "Pure Visual Basci"
"Compiling to p-code, or pseudo code, instructs VB to use an intermediate format for instructions that is between machine code and the syntax typed into the code window. When the app is executed, these p-code instructions are translated into machine code that can be executed on the processor. Compiling to native code eliminates this translation and thus can speed up execution of the application, especially when the code performs mathematicla and code-intensive operations. However, p-code executables are generaly smaller than those compiled in native code"
So, the short answer is - compile to NATIVE CODE - you can then select optimization settings such as "optimize for fast code", or "optimize for small code