I didn't mean to include EMD in the part concerning lower power supplied to the lead axle, as since EMD lacks single axle control there is no way they could do that.

"Dress" = cleaning creep (that's how I translate German Putzschlupf; I don't know if there is a British -> UIC English term) is a real benefit of single axle control - and an advantage of the 'rail-tearing' axle-hung motor Siemens EuroSprinters over the present Bombardier TRAXX locos. (There have been two major comparison tests I read of, one on the steep line to Blankenburg/Harz in Germany with its isolated 25kV/50Hz electrification, another on the Brenner route, with a DB 189 = ES64F4 coming out on top in both cases.) However, on four rather than six axles, that's still a 25% drop in adhesion. (Note that on the aforementioned Blankenburg line, the isolated electrification was dismantled in the end, and six-axle diesels took over.) Then there is sanding (and with that increased sand use and track/wheeltread wear), but that is not always stable, in particular for all four axles. There is also the cleaning brake block - which is not widespread enough across Europe for reasons that appear bureaucratic to me. And, as you say, axle weight is a third of the US, so it's all less stable. (Though still less bad for locos than for even lighter EMUs and DMUs.)

Wheel slip is just a notorious problem even with cleaning creep, sanding and cleaning brake blocks -- softwares are updated repeatedly, and they get national versions.

_{*Lunatic*, n.
One whose delusions are out of fashion.}