It does matter. But all my big displays are still LCD, because of cost.

It's about blackpoint. With an LED, pixels which are black still have a backlight. This makes them a kind of grey.

With OLED, the pixels themselves emit light. This means that black pixels are unlit.

The difference is obvious in a dimly lit room looking at dark content.

That said, while I would love OLEDs all around, they're expensive. I'm willing to give up having true blacks for the cost difference. It may be different as costs on OLED come down.

I do have an OLED phone, because Samsung is pumping out OLEDs on everything.