See it depends on your surroundings and conditions. Sometimes you dont get much time and environment to study for IIT with studies(which was my case).. so if you are determinant for IIT then it will help to get a year dropped as you will have no other studies to do and you can study IIT and IIT round the clock. So dont worry about dropping a year, IIT will make impact on your whole life so one year is a very less price to pay.
Best of luck
PathFinder
Technocrat
IIT Delhi, 2004 Batch
Currently in Student Counseling & s/w Industry