A person who's been through tough training at a 135 with a high failure rate will do extremely well at a regional, will seem much easier.
A flight instructor who goes into training expecting the worse, who is highly self motivated to learn and has excellent study habits will be pleasantly surprised.
A person who goes in thinking it will be a cake walk, who actually hasn't worked for anyone, or had an aviation job that tried to kill them, or is lazy, or has zero people skills, or is just plain stupid, will have a much harder time.