If you're using sluggish to mean higher inertial moment, then this is not a desireable trait, it contributes to PIO (Pilot Induced Oscillation), a problem most students struggle with on a well behaved aircraft.

Heavy and sluggish equate to;
- Long takeoffs runs with less tolerance for maneuvering shortly after T.O. (higher stall speed)
- Fast landings (less reaction time) and same inertial problems as mentioned above (but closer to the ground!)

Most attempt to address loading problems with a stronger engine (=more weight = higher stall speed = greater pilot lag = student being metally further behind the plane = heavier impacts = more timid student).

Lighter wing loading is one factor making a better trainer in my books. The 20mph landing speed of the Kadet is much easier on a new pilot's nerves than the 40mph mush/bounce or higher AOA required simply to maintain level flight of a plump bird.