Dear Muthuselvammsw,
As you have mentioned that you have 5 branches with 6 employee in each branch. That means, you have total of 30 employees on your company roll. So, your organization is coverable under both ESI & EPF Act. But, if you dont comply the same, the depts can recovered both the contribution amounts along with interest form the employer itself.
So, it will better for your company to take coverage under both the Act.
As all your branches are in same state, you need not to take Sub-Code in ESI. But, in future if you open a branch out of the state, then in such case for that branch, you will have to take a sub-code under ESI. Whereas, for EPF you can maintain in a single code.
Hope, I able to clear your doubt.