Ok why not.....just to be specific LOL
They are indeed very similar, but in some cases very different. Besides the planes themselves, the flight is judged a good bit differently.
IMAC is more focused on the execution of the manuever, with very critical dowgrades for things such as wings not level etc. The routines are extremely "busy", as in a lot of movement and tons of snaps.
Pattern is much more "controlled" as far as the actual flight path of the plane. you have a "box" which is 60 degrees to each side of the pilot and 60 drgrees up. Anything outside of that box is severely downgraded....like 2 points for every quarter of the manuever that is outside of the box poles. Also there is a very strict center, as in there is a pole and you better split it...or get severely downgraded. You have to do your entire routine minus take off and landing within this box at a parallel line 150 meters in front of you. In AMA pattern, the take offs and landings are scored as well.
Other than that, a loop is still supposed to be a circle, a roll should be on a rail, you get the idea.
IMAC and pattern planes fly EXTREMELY well. they are designed to take as much load off the pilot as possible. here is where pattern has the edge because inside of that 2 meter box and 11 lb limit your plane must fit, anything goes...and I mean darn near anything. This has lead to some really innovative aerodynamic limit-pushing to get the plane to fly as neutral as possible in all angles of flight, and that includes knife egde. IMAC has to stay "scale", so they are somewhat more limited in that aspect. but some of the newer designs are really testing that
To me modern pattern planes fly better than anything else out there. I like the IMAC stuff too, but since I am a builder and desinger, I get a real kick out of pushing that envelope in search of the perfect plane.
As far as the excitement factor: BOTH are not a spectator sport. It's a participant's sport (or hobby, passtime, addiction, whatever LOL). personally I find 3d to be MUCH more boring than pattern or IMAC. Fun? Absolutely!! But not nearly as challenging as trying to nail that perfect flight in a gusty 30mph crosswind. So if it's boring to you, well, don't bother with it. It's probably just not your thing and that's fine. I will say that in other countries, pattern type contests ge ta LOT more spectators than a regular fly in sort of thing. I think America is just jaded that way. And that's fine too, all that matters is that I enjoy it, and so do my friends, and new people every day.
But to sum up...it's something that if you're interested in at all, you have to DO it, not just watch because you may never "get it" by just watching. it takes a certain personality type to WANT to try and fly a perfect circle dead on center and wind corrected in a strong wind, when everyone else at the field packed up already. if you're not "that guy", just keep on boring holes in the sky and doing whatever is fun to you. but if you ARE that guy, I would greatly stress that you should pick an IMAC or pattern plane, go out and practice, and then just go to a contest. And say hello to the most addicting thing in life......