Looking at past landing missions on small bodies such as Eros, Itokawa and 67P I found different landing strategies
- Eros: NEAR Shoemaker probe performed 4 impulsive pre-planned open-loop maneuvers to land and slow down the vehicle.
- Itokawa: Hayabusa probe performed optical based navigation using impulsive feedback to a previously released target marker on the surface.
- 67P: Philae was released from Rosetta and followed a ballistic trajectory till it makes touchdown with the comet.
Seeing this type of approaches I wonder why two of them have propulsive effort (Near, Hayabusa) and the other (Philae) followed a ballistic trajectory? I think it has to be related with the small-bodies masses (escapes velocities), however, Itokawa mass ($10^{10}$ kg) is lower than 67P mass ($10^{13}$ kg). Are there also some safety issues such as fear of thruster malfunctioning?.
EXTRA: for what conditions continuous thrust (I have not seen this approach although is the one employed for planetary descents) or impulsive burns or ballistic descent trajectories is chosen amongst the others?