The decision will be proved good or bad depending upon the effort you put in. It is definitely worth it if you score well in CAT. There are people who score 100 percentile in their first attempt. However having 3+ years of work ex, you should also look at the option of GMAT. All the best!

Preparing for CAT is a wise decision ,you need to intensively prepare yourself for the national level ex.As you know its the most prestigious one so you need to prepare well.