One of the first things a person needs to do before embarking on his preparation for CAT is an honest assessment of where he stands now.
This can be done through a Diagnostic Test. It simply means taking a mock full length CAT test (frm IMS, any CAT preparation guide etc.). Purpose is to see where you stand today and what are the areas where you need to focus your energy on.
Often the areas get split into three sections - Verbal, Numerical and Analytical. From your diagnostic test you’d know where your strengths lie. Also, you’d know what are your weaknesses.
If verbal ability is an issue then start with brushing your grammar and basic English language fundamentals. Wren & Martin is a helpful book.
If reading Comprehension is an issue then start with reading newspaper editorials - Eco Times, Hindu and Times of India are good reading. Idea is to increase your speed while improving your comprehension. Often these two move in opposite directions.
If according to your diagnostic test, you find numerical ability to be an issue - see which particular area: is it algebra, series, fractions, permutations or probability. The more you narrow down your problem area, the easier it is for you to go to a text book, brush your fundamentals on that topic.
Here, its important to stress that more important than taking a test is analysing your performance. Its not enough to take a test and be satisfied with your score. Improvement comes from analysing your mistakes, reading through the relevant material and ensuring that you don’t repeat those mistakes.
Ok, all the above need to start a year before you plan to take CAT. On the question of which is a better course, I feel all do the job since how you prepare is more important than what are the specific tests you take. However, I used IMS and found it good - so you can decide.
CAT is high pressure but if the preparation is handled with proper planning and regular ’’brushing your fundamentals’’ to ’’avoid repeating mistakes’’ - you can crack it!