Between these, I would go for the Katana MiniX or Spark Mini.
I had a Spark 40 and was not impressed with it, but I have heard the Spark Mini is better.
I think the choice between the Katana Mini X and the Spark Mini depends on how “app focused” you are.
If you love using apps and don’t mind having to launch the app on your phone and connect it to the amp in order to control the tones on the amp, then the Spark Mini will give you a wider range of effects and amp models than the Katana Mini X.
If, on the other hand,. you like physical controls and don’t want to use an app, or if you want some effects and models but might get overwhelmed if there are too many to choose from, then the Katana Mini X is a better choice.
Note that the Katana Mini X has no app, and has a fairly limited number of amp models and effects (3 amp models and 10 effects) compared to the Spark mini (42 amp models and 50 effects)
IMO, that can be a good thing.
I can understand wanting to explore tones without having to buy extra stuff, but others have mentioned the dangers of “chasing tone” and, frankly, as a beginner, you aren’t going to know whether you want a “Marshall Super Lead 100” or a “Bogner Ecstasy 101” even before you start playing with the gain and EQ controls on the amps themselves.
And, as a newbie, if you want a delay effect, do you really want to have to audition 7 of them which, if you do it properly, would take several minutes each.
You can waste a lot of time doing that and, in practice, you won’t use 90% of them.
IMO the Katana Mini X is a good compromise: enough decent effects for a newbie (or even an experienced player) to explore and to have options for songs, but not so many that it becomes overwhelming. Plus, they are easily selected from physical controls, so you don’t have to negotiate an app all the time.
Cheers,
Keith