GL.Inet products that use Mediatek chipsets are great since you can usually flash standard OpenWRT on them. I would avoid routers with different chipsets since they are unlikely to get proper support.
(Though I can’t say that my MT-6000 is cheap, but it is an extremely capable router. That is top of the line though, they have cheaper stuff.)
Yeah, the Flint 3 seems like a worse overall router when it comes to computational power and chipset. The only thing it has going for it is WiFi 7 (instead of 6) and 2.5 G ethernet on all ports. The Flint 3 is also more power hungry, which isn’t great given the high energy costs in Europe.
Most people don’t benefit from WiFi 7 (WiFi 6 is already good enough for almost everything) and if you want more than 2x 2.5G ports, consider getting a (managed) switch to extend the router with.