Insulin pen or insulin pump which is better?

Depends on you. Taking Insulin by injection or by pump are both good options. There are very many well-controlled people with diabetes who do each. The primary question is which of the two ways of delivering Insulin will work best for you. People like using Insulin pumps because it simplifies the math associated with accurate testing and because it offers more flexibility in hour by hour and day by day dosing. People like injections because they are simpler and do not require being tethered to a device all the time.