You have to be careful you aren't comparing apples to oranges. You might be looking at the Meteoblue MOS (statistically corrected) predictions which might be based on their regional weather simulation. This regional simulation might be nested in a larger global model, probably from ECMWF. If you compare this ECMWF model to GFS, then you are comparing apples with apples.

I find global models like GFS are great for understanding the large scale weather systems. The regional high-resolution models, which are usually nested in a global model, give better definition of local weather phenomena like wind shadows or cooler temperatures in valleys.

Dues to averaging, weather simulations usually have a bias error in temperature predictions. These errors are corrected using statistics (look up Model-Output-Statistics) but is hyper-local, i.e., you loose the big picture. This is probably what you're looking at with Meteoblue.