If we consider shortest distance only, then depends on the starting point.
1. From Punggol East >>> KPE route is shorter (connecting to KPE from Sengkang East Drive).
2. If you are nearer to TPE exit, then TPE is the better option.
All things considered, I understand morning traffic is heavy along KPE and speed limit is only 70kph. So maybe Option 2 is better in general but not always.