i have a rear rack for swift.. accomodates 2 bikes easily but 3 is asking for trouble.. with 3 bikes one of them seem to protrude beyond the width..roof top ones are advisable if you plan to be hassle free without stressing to look out for trouble on the side mirrors.. and definitely suggested if the bikes are carbon fibre...also the rear racks cause scratches on the frames and hence the car needs to be dead slow on speed breakers to avoid damagin the bikes..
roof top ones options are Thule 20k+ for 1 bike but <30k for 2.
Kynkyny racing also makes roof top one(<17k for 2) in which the front wheel comes off; bikes is stable and completely safe this way..problem is the space reqd for the front wheel..
am going to fix the roof rack from Kynkyny very very soon..and also continue to have the rear rack for additional requirement..so this way i plan to carry 5 bikes..3 on top and 2 behind if required..
Regards