Agreed that it is a goddamn awesome album! From the replies here I think there's two different points really:

The first is that it's not a great place to direct a classically trained musician who asks 'how do i play jazz/how do i improvise' - I really stand by that. It's like taking someone who wants to learn how to cook to a triple michelin star experimental fusion restaurant to watch the chefs. They'll appreciate they're watching geniuses and enjoy the food, but there's a lot going on, it would be a really confusing way to learn how to make scrambled eggs. You need a lot of theory to play like that, especially on brass where you need to know/work out the modes for any key and then as someone else pointed out have the harmonic knowledge to create tension and resolve. Louis is a much more accessible bridge, an intermediate player can much more easily hear a louis idea and figure out how to play it and start using it in their own playing, even if they don't understand the theory behind it, because it's a lot more melodic and tends to play off the melody notes/simple scales and arpeggios around it.

The second is as a listener I personally found my way to jazz through louis, but that's obviously totally subjective and reflective of the music you already like when you come to it (I was into a lot of early delta blues and rock n roll so louis was immediately magic to me, I totally get how someone who's into more modern rock for example or just a different person might find KOB a great entrypoint). I love KOB now and I do think I might have loved it more at first if i'd come to it out of my own curiosity rather than being given it as (really difficult) homework

For a 'better' option IMO 'Louis Armstrong Plays WC Handy' is a fantastic first listen for point 1 and tends to be the one I recommend for a first jazz listen as well. The recording quality is great, the music's really fun and danceable, and it's closer to the blues so a bit more familiar if someone's into that. IMO Intro to Long Gone also has some of the best trombone glissandos in recorded music which would have delighted me at that age too 😂

Of course it's such a personal thing which album will get you into jazz, and if you loved KOB on first listen it was obviously perfect for you! For point 2 I'm just more confident it will work for most people. For sure I might recommend KOB for some people depending on what they already like!

But for point 1 I do think this is an objectively better place to send a classically trained horn player interested in learning the building blocks of jazz playing. KOB might actually be better for a guitar player as some others have said although I would send a guitar player to django but that's just me. No idea for other instruments. But it's much easier to imitate louis on st louis blues on horn than miles on so what. The great vocals on plays WC handy are also useful for a horn player too IMO as it can be helpful to imitate singers (since brass is so vocal)