RE: IMAC vs Pattern
I fly both Pattern (recent addiction) and IMAC (old addiction). I have more time flying IMAC but want to do more Pattern.
Both are great.
There has never been a 20% deviation from scale. 10% has been and is the rule since I've been flying IMAC (10+ years).
I haven't flown any of the cutting edge pattern planes- I am flying a ZN Line Supreme with an OS140RX. It is an awesome flying plane. Having said that, my 40% Carden 300 with a ZDZ Super160 flies better (my opinion)- maybe I'm just more use to it. Easier to see, slower, better power to weight (believe it or not), snaps better- everything is just more solid. Maybe if I was flying the "latest design" pattern plane with tricked out electric propulsion or YS 170 I might feel different. Pattern plane definitely flies better than my 35% Extra and smaller planes.
IMAC plane is clearly more of a pain in the rear to deal with when transporting, setting up, tearing down, storage, etc.
To me the main difference, other than the planes, is the sequences. Pattern sequences are simpler- not saying that they are easier to fly- but have more simple elements. There is a greater concentration on the shape and flow of the sequence. IMAC has lots of snaps and complicated manuevers and a new sequence every year. I have lamented that I don't have enough time to learn to fly the sequence as well as I'd like. IMAC also has unknowns in all but the entry level class. That's fun.
Both Pattern and IMAC are great. The two disciplines are close relatives. You can't go wrong with either.