If it's a work out you want Mike is spot on.
As a rule of thumb , longer boats witgh the same displacement are
generally faster. There are exceptions always.
You may be swapping speed and tracking fonr initial stability.
For scooting about a pond and a work out I am not sure it matters.
Alex

OK, here I found some interesting comparison regarding speed...

"The speed I get from the Manitou is also good. Since I can't
accurately factor for wind, current and waves, all I can do is give my
honest opinion/comparison which is that at my average
cruising/daypaddling speed of 3.2-3.8 mph, the effort is no different
between the Manitou and the QCC. The manitou starts to need a bit more
effort at my workout pace which is around 3.8-4.5. After around 4.5 mph
the bow seems to plunge a bit. I never could quite get 5 mph to show on
the GPS, but then I don't plan to race it, I just wanted to see if the
manitou could keep up, and I think it does. For day paddling purposes,
the Manitou performance, stability, and comfort is a 10."

The QCC I believe are full size kayaks so go and figure.