RE: Pattern or IMAC
Ford / Chev
It really is a question that can't be answered for you by others.
Both disciplines tend to have a great bunch of people who will help out a beginner. both require "Thumbskills" Both are fun to do.
What sorts of planes do you prefer to fly?
What sort of flying do you prefer?
Do you prefer to fly fast or slow?
Do you prefer to land fast or slow?
My opinion is that IMAC is easier than F3A at beginner level because the "normal" IMAC styles of planes (Extras, Yaks etc) tend to give the pilot the feeling of flyig slower and are less "slippery" in the air. Typical F3A planes tend to be more slippery.
However
Both disciplines will usually encourage people to fly whatever they have in the lower classes so why not give both a try a few times and see which you prefer.