None, really. Prusa printers are good enough though. If you value freedom and privacy, its worth a few extra dollars.
I've got an a1 mini myself, and I'm not aware of anything comparable on the market, but there's a clear need for some competition now.
It's a much more interesting and dynamic place than before Bambu's market entry
But you raise a good issue: are they selling these at a loss in order to leverage some sort of lock-in? If that's the reason they're so cheap, that's important to know.
I honestly wouldn't mind paying twice as much for something that's more open. But it's also an issue I haven't looked very deeply into. For my first 3d printer I just wanted something cheap and foolproof.
Have you looked into Centauri Carbon ?
The Mk3 is also easy, and can be had for cheap now, but it doesn't have auto Z-adjust which is really nice. It's also noticeably slower compared to the latest models.
[1] https://store.creality.com/products/k2-k2-combo-3d-printer-l...