Mesh typically sends/receives only what is necessary to each node and to each connected unit, which reduces noise and interference.

Extenders send everything everywhere all at once, lots of noise, they have no smartness with regards to who is connected where.

I’m not sure what a router bridge is.

In my own anecdotal experience, extenders were garbage for overall throughput, but yeah, they cost quite a bit less. My current mesh gets anywhere from 450-950mbps across 3ish acres of coverage which is more than sufficient.

Hopping. In a mesh, your device is “transferred” to the nearer/stronger signal even if there is still a weak signal from the original AP. In an extender, as long as the AP is detectable, your device will cling to it, which may result in suboptimal signal and speeds.