What method should I choose for installing Mastercam X2?

When installing Mastercam X2, the installation will scan the computer for Mastercam X MR2. If it is present, the following dialog appears, prompting you to either replace Mastercam X MR2, or install Mastercam X2 side-by-side with Mastercam X MR2:
 

If you choose to Replace Previous Version, the installation will uninstall Mastercam X MR2:

Any customized file types, such as *.mcx, *.kmp, *.mtb, *.mmd, *.control, *.pst, and so on, are left in the Mastercam X MR2 installation directory. If you install Mastercam X2 in the same directory where Mastercam X MR2 previously existed, these customized files will not be overwritten. Mastercam X2 will then be installed to the directory you specify.

If you choose to Leave Previous Version, instead of replacing your prior version of Mastercam X, Mastercam X2 is installed to a separate installation location on your local hard drive. The default is \mcamx2\. However, you can change it and install Mastercam X2 to any directory other than that of a previous version of Mastercam X. If the Mastercam X MR2 directory is selected accidentally, the following warning message appears, preventing Mastercam X2 from overwriting the previous version:

When the Mastercam X2 installation is complete, the Migration Utility prompts you to choose whether to migrate your customized files, or use the Mastercam X2 defaults.

If you choose Yes, the Migration Utility imports all of your customized files from Mastercam X MR2 into Mastercam X2. Files from any version of Mastercam other than Mastercam X MR2 CANNOT be migrated into Mastercam X2.