The overall times when looked at during actual sim time suggests Mercedes is about 1 second off the McLaren for pure race pace.
The fuel load variance could also be a factor as Mercedes will want to have tested Tyre degradation to its maximum...meaning running fatter around Barca.
There was clearly some work going on with all the antennae connected to Both W03 cars, but especially Schumacher's.
There has been some tinkering around the rear and the diffuser, I cannot find the pics, but will post it once I can find an unwatermarked copy.
The suspension component materials also look to have changed around the rear, Mercedes obviously trying to shift some mass away from the rear, to protect its tyres.
Ahh found one...
Also remarkable that Mercedes do not have the de rigour
rear tail skirts as found on Most front running teams cars.
Compared to McLaren.