Both yes and no. They are not noticably contrastier, and certainly not compared to modern multicoated lenses. However the Lanthanum glass made some corrections far easier, so that the first APO Lanthanum lenses had far better colour correction than anything made before. So the focus is in a way more precise...

I do know that I have a 150/4.5 APO-Lanthar with a deep scratch on the rear element that is still my best 4x5" lens. I won't claim it's sharper, contrastier, or in any measyrable way "better" than other lenses, yet I find the pictures shot with it more pleasing. I have compared it to several other lenses, and there really is something special about it!