I'm a rookie in both camps. Competition is the name of the game in both. Rules are a bit different, but as the man says, basic loops, rolls, spins & snaps are common to both. IMAC rules require a model to be within 10% scale of a full-scale aerobatic plane, so the popular models are Extras, CAPs, Sukhois, Yaks, Edges, etc. Go to an IMAC meet and what you'll see on the field is mostly 1/3 scale on up to 40, 42, 45%, mostly twin cylinder gas powered. They will have transparent canopies with visible dummy pilot and instrument panel, because that's what scale models are. Pattern models are typically not scale to any full-size aircraft, but rather designed in pursuit of the elusive goal of no rudder coupling to ailerons, elevator or throttle.

Go to a pattern meet and what you will mostly see is wingspans 78" or slightly less, fuselages 78" long (long tail moment), very sleek in appearance, fish-like silhouette, virtually all with inverted single cylinder two-strokes (Webra, OS, Mintor) pumped and piped for power, or YS 4-strokes, also inverted, still with muffler pipe; canopy opaque, no pilot, no instrument panel. Pattern planes are limited to 5 kilograms dry weight (11 pounds), so most of them are molded fiberglass or carbon/kevlar composite fuselage, looking for precise form with high strength to weight. Of course the IMAC planes have also gone over to composite ARFs as well, but there are many ARFs in both categories still made from built-up balsa & ply (and they fly well too).

I know a fair number of guys who have switched from pattern to IMAC or vice versa, and they all have their reasons. I fly both because I like them both, and there are not a lot of competitions in either category easily driveable from southern NH. If either one of them were to become popular to the point where I could make half a dozen meets a year, I'd probably fly that exclusively, whichever one it might be, because the standard of competition really calls for a lot of work setting up your plane, and a lot of practice once you have it set up. Flying both IMAC and pattern is OK for an entry-level flyer like myself, but anyone flying in the upper classes is not likely to want to split his time and energy two ways. One is more than enough of a challenge.

Anyway, there is a definite difference in design criteria between the two, one based on full scale, the other based on whatever design the genius types think will be light, strong and neutral in flight behavior. When I say geniuses, I am not being flip, but speak with serious admiration for the knowledge and effort that goes into these designs.

As to personality types...! What can I say? These guys are serious competitors, but at the same time they are decent, sociable people who will give each other the shirt off their back. Many stories of lending each other parts, spare engines, whole airplanes to finish a competition with. One hears the occasional dig about the other side, but this sort of talk is mostly within the lodge. What I see is the veteran IMAC flyers have complete respect for the pattern persuasion, and vice versa. It's maybe like Formula One vs. stock cars--somewhat different styles, but both serious endeavors. There is a tremendous amount of emotional energy invested in this kind of "fun", and in times of stress I guess people will say things that may be misinterpreted.

The IMAC crowd seems to be more 3D oriented than the pattern people. Most IMAC planes are rigged to do 3D, and the Artistic Aerobatics part of an IMAC meet is heavy on 3D maneuvers. This sort of thing is totally absent from a pattern meet-- at least as far as the official program. But after the rounds are finished for the day, pattern guys will get out their foamies and Funtanas or whatever for recreational flying.

The pattern crowd is experimenting with electric power in a serious way, but I doubt that will ever spread to IMAC.

Pattern old-timers complain about the shrinking contest calendar, loss of pattern-friendly fields, the high and rising cost of entry, competition rules that seem to get harder to interpret every year. IMAC seems to have benefited greatly from the availability of big ARFs, so you don't have to spend two years putting a plane together. You don't have to spend thousands of dollar to join the fun, but deep pockets certainly help--especially in IMAC with their $2000 power plants, 10 or 12 servos at $100 apiece. And of course a $2000 radio will help make you feel like one of the guys. I doubt I will ever get to that stage...but if I were younger, flush with cash and energy, had plenty of free time in my schedule and had a well-organized household, I could be tempted! Then don't forget the trailer and mobile home! No question about it, America is a wonderful country. (What!? Me?! Jealous?!)

Seriously, there is plenty to admire in both camps, speaking of the people, their equipment, knowledge and flying ability.