Decapeptyl is cheaper (although there's not a lot in it).
Decapeptyl is also available as a 24 week dose, which means fewer visits into healthcare establishments, which is a significant factor during COVID-19.
My hospital and GP prefer Zoladex, and it seems to have fewer injection site issues compared with Prostap and Decapeptyl, from what I hear from others on them.
I learned to do my own Zoladex injections, which solved the problem of visits into healthcare establishments, although I actually did it so I wasn't going to find it being done by someone who didn't know how to do it. That never happened to me, but I know several people where it has.