Switching from syringes to pens was a bigger decision than I expected

I've been comparing insulin pens with vials and syringes, and I am trying to understand which option makes more sense for different situations.

Pens seem more convenient, but vials and syringes may have cost advantages depending on the person's needs and access. I'm curious how people decide between them in real life.

For people who have used both methods, what differences mattered most? Was it convenience, cost, travel, ease of use, or something else?

I'm looking for practical experiences from people who have considered both options.