I believe it depends on how negative the SV is, and how close the team is to completing the project. If a negative SV was calculated closer to the beginning of the project, there is still enough time to speed up the process and catch up. It will be concerning however, if the SV was very negative near the end of the project with the deadline quickly approaching. In the latter scenario where the team is almost finished, I would choose to have a positive SV over positive CV.
If the team isn’t close to the deadline, I would rather have a positive CV to make sure the team isn’t being wasteful and overspending. It will be difficult to try and garner more funding once the original budget is set in stone. If the company doesn’t have any more money to funnel into this project, the team will need to convince stakeholders to invest more. This can lead them to lose interest and withdraw their involvement, causing the project to be dropped.