Jim Terrell's a good paddler to follow for flat water sprints. He was in 4x Olympics for C1 and now he's testing out a lot of stuff with SUP race boards. Check out his thoughts on SUP sprints (including video):
www.supracer.com/jim-terrells-sprint-sup-racing-secrets/Here's a quick comparison of times.
SUP: 13.39km/h200m (Jim Terrell, 2012 Silver Blade Regatta)
53.76 seconds
C1: 17.03km/h200m (2012 Olympic Gold Medalist)
42.29 seconds
K1: 19.86km/h200m (2012 Olympic Gold Medalist)
36.25 seconds
SpecsK1 length: 520cm
min weight: 12kg
C1 length: 520cm
min weight: 16kg
SUP length: 381cm/427cm (12'6/14'... sprints are usually 14')
weight: usually between 9-15kg
Speed differencesC1: 27% faster than SUP
K1: 48% faster than SUP
Keep in mind C1/K1 boats are longer, plus their times come from the Olympics, where the very best are competing. We've never had a flat water sprint with all the top guys (...though Jim Terrell would be pretty hard to beat no matter who was there).