If I had to choose between the two possible cases I myself would go with scenario 2. It is better to be behind schedule but under budget, than ahead of schedule and over budget. I say this because you can always work harder or get more people to work on the project if you have the money to spare, rather than being behind schedule and over the amount you can afford for the project. However, there is always an aspect that your CV may increase in order to catch up to where you should be. In a way, CV and SV factor into one another. Either way though it always better not go over your budget, unless you know for a fact that this project will cover to expenses you made that caused you to go over budget.