Ian Chappell, Bill Lawry and Ashley Mallett are on record calling Prasanna the greatest offie of all time. I don't necessarily agree but since you are keen on peer reviews I thought I would let you know. Judging Indian spin quartet (and Gupte before them) based on stats alone will be unfair because we had guys like Pataudi, Solkar, Abid Ali and Gavaskar opening the bowling to take the shine off the ball, moreover we were extremely poor catchers bar the GOAT at close in, Solkar. I know you rate Engineer very highly but based on what I have read/heard he was an awful keeper and most certainly cost us the 1969 series against the visiting Aussies. Should never have been a regular fixture ahead of Budhi Kunderan but Pataudi had his own biases.
Venkat was not in that league but the other 3 were special. Can't imagine another all spin attack plying their trade all across the globe like them, each brought something different to the table. Viv called Chandra more scary than Thommo LOL. And Bedi IMO is the GOAT SLA ahead of Underwood/Herath for reasons that go beyond stats.