Differences among Kathakali, Kootiyattam and Nangiarkoothu

[natyasri]

can someone please explain to me the difference between Kathakali, Kootiyattam and Nangiarkoothu? I want to learn just one item in either of these. Are there any teachers/help aids available along with recorded music.
Please do not misunderstand me. i have been a student of bharatanatyam for long and learnt kuchipudi as well, just want to challenge myself and learn something new to expand my knowledge base.

thank you