I would generally prefer oblique rotation when you expect at least some factors to be correlated. Oblique rotation does not force factors to be correlated, whereas orthogonal rotation does force factors to be uncorrelated.

Hello Viola,

In addition to Christian's response, please note that choice of rotation scheme has no effect on how many factors are extracted.

Extraction comes prior to rotation, so it's entirely a matter of what method (e.g., parallel analysis, scree test, a priori declaration, eigenvalue > 1) you decide to apply to making the decision as to the number of factors should be extracted.

Good luck with your work.

Thank you Christain and David Christian Geiser David Morse Your answers are really helpful :)