The negatives are better to scan since they have all the "information" intact. Prints are kind of compromised in their range of tones and highlights/shadows.
Are you having your negs done by a lab? Do they offer an affordable scan to CD option? If I shoot color, this is what I do. Scanning color is really hard...at least for me...
Edit: Just had some thinking time on this. If your ultimate goal is to make prints, then by all means, go straight for the print. If you want to digitize pictures to put on the computer, then it would be best to scan the negatives and make prints from the file you create and edit on the computer
