It sounds like you’re doing great so far. Keep it up!
The biggest difference is tire availability. If you like the rugged Duro Wildlife tire that comes standard, a 24" might be fine for you. But most of us, particular those who started later in life and who aren’t super aggressive riders, prefer a tire for muni that’s still wide but rolls more easily and isn’t as heavy. You’ll never run out of tires to try from the 26" downhill MTB world. 24" tire alternatives are fewer and mostly not as appealing.
Look over these two threads and you’ll see a difference:
A larger diameter tire is also better at rolling over bumps and rocks and roots, which also favors 26". Some have jumped straight to 29" because of this. The downside is putting yourself higher off the ground, which tends to make mounts trickier and dismounts more precarious, along with the weight of the larger tire and rim you’d be managing.
I ride a steel Nimbus muni frame. I bought it used and have done a fair amount on it. It isn’t fancy but it’s been great for me and I’ve never heard of one breaking. It’s kind of the small-block Chevy of the muni world. 