Are classic ski's
faster at double poling thanks to slightly longer ski's,
or do skating ski's hold the advantage thanks to their full glide wax job?

classic skiing is faster on double poling because the classic poles
have optimal length for parallell ski position. DB with longer poles
might feel comfortable for beginners but classic poles are best for
speed.

why some use skate skis on classic sprint is because the track was very
short and all flat. but they used classic poles anyway. (Drammen)

faster than classic on anything but very soft or sticky snow
and extremely steep climbs

and add double poling