Contract interview is generally a one stage or maximum 2 stage process (1 x Telephone interview + 1 x Face to Face interview). Permanent interviews can take weeks, sometimes months and can take up to 3 months to land a job and sometime Companies may hold your profile, untill unless they get a project for you. Contracting is all about hitting the ground running from day one whereas with permanent jobs have many Interview stages and longtime taking process
Make sure you prepare for the interview very clear. Do the research about the role, what you can bring into the organisation etc… All your interviews will focus on whether you can hit the ground running from the first day. You need to strategies yourself more towards a problem solver. They also look for your experience in different situations and for specialized skills.