Gary

A lot of factors influence performance - metal or plastic, sintered or
machined metal, machined brass or machined nickel silver, dirt or oil on
the track, pointed or shoulder journals, fat taper or narrow taper, metal
or abs or delrin sideframes, equalized vs nonequalized, sprung or unsprung...
But all else being equal, my experience is that metal wheels outlast and
outperform plastic wheels by a huge margin in HO scale. If you think about
the physics of wheels on rails, the weight of an N scale car per square
centimeter of rail contact is far less than it is for HO scale cars, so
direct performance comparisons are not meaningful between N and HO scales
(or between HO and O, or O scale and 1:1)

Then add car weight variability to all that to really confuddle things!

Tim O'Connor