Consulting companies are limited to biases as most outsourcing companies (in India ) atleast have a big degree of ex consultants.
So each consulting company seems to have a prid quo quo arrangement or a favourite partner.
Outsourcing companies themselves have a lot of churn/attrition in senior management. So nearly everyone knows what the other rates /details are.
The industry average attrition is 40% and thats the annual growth as well.
The best way to choose a consulting/outsourcing company is to
a) ask for previous case studies as for your EXACT process
b) ask them about billing/salaries ratio for their staff for the outsourcer.
c) Ask about risk manaagement or change control processes in place for terminating or transitioning ownership, or even scenarios for changing vendors .