Longer bows are more resistant to cant than short bows. They are usually the only way to get draw lengths longer than 30-31". They are easier to shoot with fingers - but that's becoming a lost art anyway.

IMO, forgiveness has less to do with bow length than with riser design. Deflex risers - where the low point in the grip is in front of the pivot point of the limbs - are inherently resistant to torque and will let you get by with some pretty bad form mistakes. Reflexed risers - where the grip is behind the pivot point of the limbs - is very susceptable to torque and will make you pay for every little form flaw.