What are the pluses and minuses to using the vcredist.exe versus the msm files to install the Visual C++ 8.0 runtime libraries?
MSM will give you a better streamline experience then vcredist, it will integrate with the progress bar and will rollback on error (or cancel).
From the developer side you will benefit by seeing the msm log in the main setup log file and it will execute its actions side by side with the setup action (with vcredist you will need to sequence it yourself).
Because of all of the above reasons I usually choose to use the msm (and its more or less one Wix liner to use it).