There is very little difference between them, in side effects or success rates. Some oncos have a preference for one over the other but it seems yours doesn’t. Men with pre-existing heart problems may be better with one than the other.
It is true that if you have one and it fails, you then cannot have the other under NICE rules, unless you get onto a trial. That’s because if abbi fails, enzo will also fail very quickly and vice versa. The exception is if you start on one and then find within 3 months that you can’t tolerate it for some reason, you are allowed to swap over.