Each one of them uses the Robellus network, and can only provide to some residential areas since that's what the CRTC can regulate.
Robellus charges them all the same price, which is why all of them have nearly identical plans - because fundamentally, they are. You get even worse technical service since Robellus controls that and they drag their feet on it (not customer service, that's often better).
CRTC has been increasingly toothless too on actually forcing competitive prices or service down. If you got recent fiber connection, you might be screwed as then there's a moratorium on Robellus being forced to share service, so you might end up with no third-party options for a while.
And if you're looking for a commercial zone connection, well, more likely than not RIP since CRTC doesn't regulate that, so you're stuck with whatever shit service at inflated prices Robellus offers.
Access to independent grocers/co-ops/etc is also not necessarily a given if you're not in the right areas. Mostly more remote areas without much local agriculture tbf, although there may be more I'm not thinking of.