I'm getting pretty far into IMAC, and am just starting some pattern work. In my limited experience, I have found that while in pattern you must be more precise to score well in the maneuvers, but in IMAC you need more skill just to get through the maneuvers. This is more true in the upper classes than the lower ones. Pattern planes are much easier to fly because they are synthetic creations designed to fly perfectly as model airplanes. IMAC planes must make do with how their full-scale counterparts were designed, with some limited adjustments. Both require a lot of practice to become good at, but the IMAC folks are at a disadvantage due to manuever requirements and aircraft design.