Hi,
I have completed MBA (ITes) in BITS-Pilani. Currently in Oracle Business Development team in bangalore. I have written CAT and BITS aptitude, so let me try comparing.
Well personally I feel CAT is not a tough test if not for the time constraint. BITS aptitude is a 60 minutes test for just 48 questions and to add to it you can take a calculator with you which again CAT doesn't allow. So you mustn't expect question as in CAT which can be cracked easily with a calculator. In fact none of the exams are comparable to BITS Aptitude test

. What BITS wants in not people who can multiply or divide quickly without a calculator

, but people who can solve problems. They need problem solvers and people who can adapt but not people who are calculators

.
Apart from the quantitative qns other qn like verbal, data sufficiency and logical reasoning are all comparable to CAT if not for the time constraints.
On the whole I would say this test selects the right person for MBA. And if you have the right aptitude for MBA then I don't see a reason why it won't be easy to crack. I found it easier than CAT.
Hope it helps in you preparation.

For more info refer
http://www.bitsadmission.com/admn/br...HDbrochure.pdf