One thing with a rear rack is if some dopey idiot runs up the back of you at a set of lights it's good bye bike least on the roof they are safe unless you encounter a car park height bar......
Tow bars to buy stand at about 100 quid and fit in about an hour with 6 bolts
The electrics are a bit more fiddley
Opening the boot is certainly a plus, but yikes, having the £££ in bikes hanging onto the roof open motorway speeds etc scares me to death
Also don't roof bars scratch the roof etc?