I have been using Vodafone and Airtel for over 4yrs now and my father, Reliance.Now, unfortunately I am leaving the Vodafone service due to unavoidable reason. I bought an iPhone and the turbo sim the iPhone needs does not accept the new sim.
Network: 3.5/5. The network has been excellent in the metros and all areas where Hutch itself serves. In basements, it is simply superb, and beats hands down, to Airtel and reliance and others. MTNL/BSNL are pathetic in basements. While on the move, Hutch/Vodafone is great except when on trains, where Airtel wins network coverage. Mumbai, Vodafone has 900Mhz spectrum and is 100 times better than Airtel, which on 1800Mhz does not have a good coverage at all. In Delhi, both are same in network coverage and quality.
Voice Clarity: 4.5/5. The voice of both Airtel and Vodafone are pretty much fine where network coverage is decent. When on low strength of network, surprisingly, Vod still has much better quality in voice than Airtel. Reliance is between the two I would say.
Customer Service: 5/5: I would say Vodafone has the best service any telecom service provider can offer in India. Idea is a distant second and Airtel is only recently getting up. Reliance remains abysmally low in this aspect. Vodafone care outlets has decent staff who at least smile and are patient with even the "Ramu kakas" in the mobile community. Airtel is improving but still not as impressive as Vodafone. This contrast is even more visible on attempting telephonic conversation with the customer care. I remember days where Airtel never connected even for 2hrs continuously. For reliance, relationship centres are decent but the staff almost always does not seem very cooperative. You need to be patient. Customer care people are really not trained well. Vodafone customer care guys speak well, are patient and polite and most importantly, trained well for their job.
Call charges: Vodafone is more expensive in this aspect and its plans are not as competitive as Airtel or Reliance. Reliance and Airtel are neck to neck in this and especially the intra-network calls, STD and local, Reliance and Airtel are pretty up there. Vodafone loses in one more aspect in this, that it does not have that great India-coverage to provide intra-network STD cheap calls etc. Idea and other small players have this drawback as well.
Value for Money: 4/5: The bottomline. Vodafone is a much better service than all others wherever its own network is. If you are mainly a local calls person, Vodafone wins hands down. Take it. Its equally cheap to others.
For STD callers, if a little more bill is also a concern, then Reliance is probably the next best bet, and Airtel alongside/thereafter. But remember, the experience may not be as smooth as Vodafone may offer overall.
P.S. Currently I am using Airtel (supported by iPhone) and its service is improving since last year. :)