Here's my answer..
If we talk about numbers, CAT really does stand out. I agree. But lets talk about GMAT's numbers as well. From India alone there are around 20,000 test takers every year. Thats a huge number. The global number is around 250,000 in a year. Lets consider the top 6 B-Schools in the US(coz we are considering the 6 IIMs here while writing CAT. Lets be fair!). There are around 1,400 merit seats in the IIMs. So they conveniently think that the selection ratio is less than 1%(Considering 225,000 CAT takers). Come on! Be real. Total seats in the top 6 B-Schools adds up to around 2,500. There are around 20,000 applicants who fight tooth and nail for these 2,500 seats. Now 20,000 applicants applying to 2,500 seats doesnt mean a selection ratio of more than 10%. The rest of the 280,000 people(280,000 because there'll be people who would have written GMAT for one season and for some reason they'll be applying with the same score in the next season as well) could have applied, but they dont because they think they are not worthy of getting into those 6 schools. Because there's an assumed cut-off in GMAT unlike CAT, where the schools determine the cut-off and then call the applicants for GD/PI, people tend to think that GD/PI is the second round. Strictly speaking, CAT is just a test and GD/PI is the first step taken by the school. This is because there's no option to apply to the IIMs after getting the CAT score based on the score. That would have been better to clear out the confusion. Now check the numbers for yourselves :)
GMAT has around 250,000 test takers and a considerable number of re-applicants fighting out for around 2500 seats in the top 6 US schools. And there are 225,000 CAT takers for 1400 seats. So now beat the number game! :)
So for all the CAT takers this year, All the best! :) Dont let the numbers affect your focus.