I recently purchased a 16Gb 4S. When I connected to iTunes it shows that, before apps, other, etc. that I only have 13Gb available. Does iOS5 take up 3Gb?
My iPhone 4 16gb shows that it has 13.7 free before anything else with iOS 5 installed. Of course some may be different from others depending on how the memory formatted. May be a different brand of memory from the 4 to 4s but I wouldn't think that it would be that different. I also don't have siri though so that may be some of the difference as well.
the hard drive and flash memory industry has been scamming us for years. you always get less than the amount advertised. the actual calculation is 1024 kb to 1 mb and 1024 mb to 1gb and so on. but they generalize it by using 1000 to 1 so they end up giving us less. the difference get worse as you go up in capacity.
The main reason as to why I was so concerned is that this is my first Apple product and had never had to use iTunes. I have a lot of music in WMA format. When I imported this to iTunes it HAD to convert it to mp3. The issue is that a 2mb WMA file converts to an almost 6mb mp3 file; I basically am tripling the amount of space needed for the same quality of song.