I was on 6MP for seven years. It really didn't keep me in any long term remission. I believe the best it did was a two year remission after taking it for about six months. I then started flaring yearly, then twice a year, and, well, you know, I had surgery June 28th of last year. Remicade failed after my 3rd infusion and Humira didn't do squat for me either.
My GI doctor took me off the 6MP two weeks before I started Remicade. He is not a believer in double dosing with the immune suppression meds.
I would give the 6MP a shot first. It does work for some people.