Walk
My uro/surgeon had me try each of the ED meds. My Rx is for Cialis, but he did find sufficient samples of Levita, Viagra, and Staxyn for me to try all multiple times.
Because they are different, I would expect to be told to try all of them before resorting to injections. You are moving from a pill that can easily be obtained (no cost discussion, just the mechanics of it) and taken, to a med that has to be custom-made at a compounding pharmacy, has a short shelf life, and has to be injected with the potential of painful ER trips and pierced urethras, as we have seen from recent poster's experiences. Yes, if you need it, and you get the system down to a science, it works where other things do not. But I assure you I would much rather have a pill that worked. No doubts there. None.
I would have more doubts about a doctor who would go straight to shots.