MattH
You can do a bit more quasi pressure profiling with a direct lever (by varying the pressure on the lever) and pulling the shot is always fun. The Flairs deliver superb espresso when done right but temperature accuracy and stability is not great other than with the Flair 58 electric, the latter which makes consistently good shots a lot easier.
The 9barista makes making superb espresso easy because it limits the variables to heat/pressure (one leads to the other so they go hand in hand) and grind size. So while it’s easy to make great espresso it’s not going to easily produce a range of styles like a direct lever could. And it has a big advantage in its smaller footprint which will be more important to some than others.
That said, I find that I generally use the same go to profile/preset/recipe for each machine. With the Nurri it’s a double ristretto, the Decent it’s a standard espresso and with the 9barista it’s… well, a 9 barista shot because it pretty much does just the one thing but dang it does it so well.
But to your question: I think that a newbie will learn more about espresso making with a Flair 58 than with a 9barista. Temperature can be changed and pressure can be varied. And you could try different basket sizes.
The 9barista is not going to give you as mush opportunity to experiment but I’d certainly recommend it as a first espresso machine for anyone who simply wanted great espresso without having to explore the rabbit hole.