I am not sure about the service of Airavat in other routes but they are the best on Mumbai-Bangalore route.
I am a frequent traveller on this route and have travelled from almost all the travels but found KSRTC the best.
Well my point are as below:
KSRTC buses are in good condition and all their volvo buses in this route are new.
Good and cooperative staff.
Very experienced drivers and that gives you a good nights sleep:)
Airavat buses maintain well timmings for both Arrival and departure.
Bus halts and good restaurents and have clean toilets so is a good especially travelling with family thought the food on these stops are on expensive side.
Your luggae is safe inside your bus whenever you step down for some refreshment. Reason - they lock the busus at every halt.
I personally prefer Airavat among others travels for its Punctuality and service and is defiantly reliable service in this route.