Which is important the team performance or the project performance?

The best Team Performance resulting the best Project performance.

Both are related you can’t find excellent team performance with weak project performance unless you as project manager measuring two different scales .

for senior management, what matters is project performance, as progress reports measures what was accomplished in the past, yet, team performance is very critical and essential to estimate where the project is at the moment and will be in the future, so project managers need to keep an eye on both.

The relationship is proportional between Team Performance & Project Performance. They come hand in hand.

The team is the backbone of a project, and are measured qualitively and quantitively.

The team performance is based on the quality of work been performed, if the performance of a team does not meet expectations, then you are missing deadlines, producing bad quality products, which would result in increasing cost to do rework and so forth, hence, will result to not meeting expectation as far as Project performance. 

The Project performance is mostly cost, and schedule driven (quantitive) and senior managers are concerned when a project performance is not meeting expectations which indicates the team is not performing in a qualitative manner.

Therefore I believe Team performance is essential to the project performance.

Good quality work = on-time deliverables= meeting budget/less cost.