I think that maybe you you got a dud or you didn't know how to use your computer properly. Your computer was actually rated a battery life of 3 hours 50 mins in speed mode to 6 hours in stamina mode.
http://66.102.9.104/search?q=cache:...0P+B+battery+4+hours&hl=en&ct=clnk&cd=3&gl=uk
With Sony you should be able to get more battery life than the rated battery life that Sony gives your laptop. My laptop was rated 3 hours in speed mode (probably in performance mode with full brightness) to 6 hours in stamina mode.
Also you had the low entry model with a smaller capacity battery and not a premium black model with an LED screen which was also a bit lighter.
You claim that the MBA has better performance but just look at these test results here they do not back up what you are claiming. The battery life test was also done in speed mode and not stamina mode-
http://www.pcmag.com/image_popup/0,1871,iid=217459,00.asp
I own a premium SZ7/C and can get over 6 hours battery life with wifi on using 30% brightness in stamina mode in power saver. I should be able to pull of at least close to 7 hours with wifi of just doing office work.
I don't think that the MBA can get quite as much battery life as that.
I don't use any anti virus because i am careful about what i download.
Getting back to the topic though i don't hate the MBA i have owned about 4 Mac laptops but don't currently as there is none right for me. I would have liked the MBA to have been a smaller MBP instead and then i would have bought one. I tried a MB but they were not right for me.
Just look at the specs of the new Sony Z the premium SZ's replacement. The Z weighs 3.3lbs and the specs are great. For me Apple's portable range is a bit lacking.
I don't know what you are trying to say by your last sentence. The SZ model that I had was SONY VAIO SZ 320 P/B. It is not a premium version of the SZ and I bought it last December 2006. Here is the link for the tech specshttp://esupport.sony.com/US/perl/model-documents.pl?mdl=VGNSZ320PB. When I bought this computer I clearly remember that advertised battery life for it was 3 hours only. In which case it usually last for 2.5 with normal usage.