yeah this I posted on the former DFI once, it's from the book Balidaan. 9 Para and MARCOS did this joint exercise but see, MARCOS began changing after 2008, alot has changed now. Old school Para were a bread apart and Mahendra worked with John De Britto, Sudhir Walia, Jasrotia, etc... even Major Jacob and Ln Naik Mohan Nath Goswami. Dude has been at the top of the game. By the way he did mention that everyone's a master in their own domain.
"Navy SF guys are better in water and Army SF is better on land" this shows that it's the same operative now if you keep him exposed to water for longer part of his career that's his speciality right there, if you keep him exposed to CQB / Anti hijacking scenarios for longer and make his equipment and training for that specifically you'd be NSG, keep the same type of guy in deserts, you have 10 Para, and so and so. 21 is for NE, 9 is for Kashmir. They all are deadly in combat but the environment they specialize in determines alot.