Workflow-wise it’s more refined and an absolute joy to work with, if you clicked with the Mono you’ll be flying around the interface in no time.
All focus is on that single synthesis type so there’s less to learn, I imagine that users struggling to get their head around the A4 are new to Elektron products, those who’ve used the other machines, beforehand, tend to say that the A4 is the easiest to understand/use.