Summary: Don't use the Credit Card as long as you have another option.
A couple of days ago, I personally visited the train ticket booking counter to do some bulk ticket purchasing. Now, in Chennai Central Suburban Reservation Complex, I found that the credit card and bulk booking counters on floor 2 were quite empty and was pleasantly surprised at the teeny-weeny queue of about 3-4 people in these.
Only when I'd approached the counter did I understand why. Credit cards get charged an additional Rs.30 per ticket (6 people max in each ticket). While that's ok for a small number, if you have to do a huge bulk booking, it can become not so comfortable.
On top of that, your credit card company may additionally charge 2.5% on the entire transaction !!
The tough part is that if you have to cancel any of the names on the ticket, the card holder has to once again personally visit the counter. Tough luck !