I would normally say that for storms like this out in the middle of nowhere for awhile, I think a lack of obs is why in general they would normally be more off, the both of them.
For this storm though, we do actually have some recon data. I don't know what data gets fed into the GFS that the Euro might not get though. Recon data may include not only something like sondes but maybe even radar data too. I'm not sure. If so, and the Euro doesn't get it, then it might have an advantage.
I don't really know how the GFS and Euro ensembles differ. Conditions are tweaked as far as I understand between members. Is it always the same? Are the Euro members tweaked more? I just don't know.