your opinion

In your opinion, is it better to have a team with team members who are very similar to each other (similar background, competences, culture), or a team where there are lots of differences between team members?

It is typically easier for people to relate with those who are similar to them. Communication turns out to be easier (it is possible to understand each other "with not many words"), the chance for misunderstanding is small, and therefore the chance for conflict as well.

On the other hand, a group made up of similar people is often very strong in an area, but "blind" in another one. For instance, a team made up of analytic people who love detail and perfection risks losing a sense for the whole.