Flyerguy, you`re correct with regards to the wake vortex categories. Although the ATR 42 is light in the UK but Medium elsewhere (ICAO).
The term heavy in this context (career paths) is just to differentiate light turboprops (King Air + Jetstreams) with the heavy glass cockpit passenger service TP`s (Dash 8 Q400 + ATR 72-600), i.e greater than 20 tonnes. Funny enough some pilots can get caught out flying a heavy ATR 72-500/600 (6 bladed props) which can be difficult to slow down if not anticipated correctly leading to unstable approach and go-around. Introduce even heavier TP's such as the ATR 92 (if it eventually gets the go ahead from Airbus), increased blades, swept wings, winglets etc. These nextgen TP's will actually be closer to a geared turbofan.The point I`m making here is that the gap between the nextgen TP's and turbofans is actually reducing now that TP's are really back in business.