The DG will perform better, about 2 L/D points especially so when ballasted, has a higher max wing loading.

Libelle
LD 34.5
Max loading 35.7kg/sq M at
Empty weight 200Kg
Max weight 350kg

DG 100
LD 36.5
Max loading 38kg/sq m
Empty weight 230kg
Max weight 418kg

Libelles suffer from a lack of rudder authority when rolling quickly at low speed, but are easy to rig.
They also have balsa core wings, rather than foam.

Its worth reading Richard Johnsons flight test of the DG100.
https://scalesoaring.co.uk/GLASS/Doc...%20DG-101G.pdf
Fixed tail and elevator is the best model.
The fuselage is 800mm longer on the DG, the longer tail and larger rudder and elevator moment imparts good stability
If you fly a lot in weak conditions, lean towards the lighter weight Libelle.
Regards
Dave L