Dude I think you underestimate the other. Marcos entered the OP in Mumbai and nailed everybody they could find without any loss of life, they were the first ones to mop up the OP they were assigned to while NSG was still busy with the other areas. The mission was 100/100 for them. Secondly, Marcos operators are deployed near many lakes and rivers in the Valley. They are certainly trained in HAWS, doesn't mean they are the best for that role but they certainly are trained there. Marcos are also trained at CIJWS and desert warfare school in rajasthan. SFF is a different breed and doesn't always have Para SF members rather members that are trained to be in SFF since the start, offcourse there are a few who come from different units but SFF is a Special Mission dedicated to covert missions working closely with RAW. SFF/ Garuds are also trained in amphibious ops, they are not trained to expert level but they can certainly handle dives and combat operations in marine environments.
Para SF personnel being invincible is good thing but it would be a sad day for any one to underestimate Garuds or Marcos. Their training these days is more or less equalized with different services focusing on their prime areas but also since the start inculcating harsh training in the most diverse conditions. the kit they deploy is also steadily getting better. Its also really silly to be comparing Parvat Ghataks to a Marine Co, they are meant for different roles, the same parvat ghatak would have a tough time conducting a long range deep scuba dive infil op deployed from a sub, doesn't mean they can't but they are not trained primarily for that. All these units have roughly the same length of training and are trained in various prestigous schools in the country.
A Delta operator would have a tough time matching a ST6 operator in the water.
All Indian SF units old and new are pretty good and among the most well trained, it is in the end how they are deployed that makes the difference. The IA at the moment has the worst doctrine of deployment of SF units among the 3 services which actually doesn't surely use the skill to good effect. Garuds/ Marcos have a better role/ deployement doctrine which will allow IN/IAF to use them against an enemy where it really hurts.
One can say indeed the 9 Para-SF are great warriors for their roles but I am sure a Gurkha or a Ladakh scout is even a better warrior of the mountains, there is one thing being trained to fight in the mountains and there is another being born there and trained to rule there since birth.
Now from what we also know between SFF/ Marcos/ Para SF/ NSG and Garuds, there seem to be additonal special teams within each force i.e the ultra elite in case of the NSG revealed recently is the so called Phantom Unit i.e 1 percenters who are sent out for highly classified additional training.