videoreader readframe with 'native' option returns the usual cdata and colormap information . without the native option ind2rgb equivalent is automatically done returning the rgb version of the data .
The change was for efficiency . With aviread it always scanned the full file at the time it opened it and the buffer flow was not as good so it was slower and took more memory . The newer function is better for streaming type situations especially with larger videos that might not even fit in memory .