I think the main benefit of the infant seat, especially when they’re really little is the transportability. If you won’t mind being able to carry them in and out in the seat you should be fine!
I just switched my 6 1/2 months old to the convertible, because she is bigger now and sits up. So when we go out places she is big enough to sit in the front of the shopping cart and i could use a regular stroller. You just have to be willing to carry baby in arms in and out convertible . Because that car seat convertible is meant to stay in the car vs the infant car seat.
They are both safe. I always recommend new mommas to get a infant car seat for the first few months just because some babies can come out really small and a convertible is just too big but if your boy is 6 months in my opinion I don’t see anything wrong with switching to a convertible