Helo-watt,
Welcome to the addiction. Hopefully we can help you get up and in the air. Seeing the above statement should speak volumes. The people with no experience are saying this, but you have to remember that they have no point of reference to base their statements on. Listen to the instructor you've spoken too. The planes that you are considering aren't very good trainers. The decathlon is a very maneuverable plane and can be a handful for a beginner. Also, Cubs are notoriously tricky to fly and once again can be a handful. On your side though, because they are park flyers they will fly slower and tend to have less damage when crashed than bigger models do.

My recommendations would be to try and find a plane designed as a trainer. As an instructor I can't even begin to count how many times I've had new people show up at the field wanting to learn on planes that aren't trainers. The instructors that are telling you that the plane isn't a good choice aren't trying to be mean, they are just telling you that the plane you have chosen isn't a good plane to learn to fly on.

Hope this helps

Ken