As CVI was released (1987) before the ANSI-C standard came out (1989) perhaps the question should be the other way round!
In those early days, CVI was intended to be multi-platform, so it made sense to develop a set of libraries that operated in the same way across the various computers that it was targetted at. These days, focus seems to be mainly on Windows, so this early philosophy is somewhat redundant, especially, as you say, with the widespread adoption of ANSI-C.
Personally, if there are similar functions in CVI and ANSI, I will go for the ANSI ones every time for portability reasons, but then again I write code in a number of different programming environments.
JR
