This is HDFC Classic Banking program, In which You will get some features like lifetime free debit card, Zero MAB NON-MAINTENANCE charges, free ATM transactions and free money transfers.
To Be Eligible for this one need to maintain 1 lakh then he/she will be eligible for classic Banking, Still many gets upgrade if they just have good transactions. There is no MAB non-maintenance charges, So if you will not maintain the MAB, you will not be charged.
Also If you will upgrade and if you have good transactions in a month then it will not be downgraded.
Infact no-one gets downgrade from it, I had never seen anyone getting downgrade from classic banking.
My suggestions would be upgrade it and just maintain 1 lakh for 3 months (As this is the period where your account is under review)
So yeah there is not much Benefits but still you can upgrade it.