In meantime I tried as well several Hotels in Madrid.
The worst (up to now) was the
Marriott Courtyard Princesa. When I stayed there the 1st time some years ago almost the complete team was on strike. Furthermore they have many tourist groups and you can have a lot of traffic noise if your room is facing the street. Basic price rooms are not renovated yet (they bathroom anyway not).
The
Marriott Auditorium at the Aiport is qute nice (with nice Executive Lounge) but its too fare away from everything. I would only take it if you want to say a night before or after a flight.
Some weeks ago I stayed in the
Indigo GranVia. Small rooms but very nice breakfast. Almost no noise from the streets but currently they have some construction in the building next to the Hotel ongoing. However the Roof Top Bar is Excellent and open for everybody :-) You can reach most of the points (SOL, Palace Real ...) by walking.