Dear Student,
I would like to tell you that b.com and bba are two different fields. It cannot be said as if one is better than other.Both have their own course and their importance respectively.Its your choice for which course you want to go. If you want to have knowledge about marketing,finance,economics,statistics at the same time B.com would be a better option. If you want to have knowledge regarding Business Management and Business Administration BBA would be a better option for you. After b.com you can specialise in one subject in M.com. After BBA you can easily do MBA.
All the best. I hope this was helpful to you.