[*] Why are Gaming Headsets often said to be inferior to regular headphones?
In general, headphones (especially "audiophile" or "hi-fi" headphones) tend to have better sound quality than your typical gaming headsets. This is due to a number of reasons, such as: a design more focused on maximizing sound quality instead of maximizing stylish "gaming" looks, an Open Vs. Closed design (most gaming headsets are closed), and simply having moreexperience at designing headphones than gaming headset companies.
[*] What about multi-driver "true surround sound" headphones? Aren't they better?
No. Multi-driver headphones make use of tiny drivers with inferior performance to larger stereo (dual driver) headphones. A better route is a good pair of stereo headphones with a good virtual surround DSP.
[*] Will headphone X be a huge improvemet for competitve gaming over the AD700?
Probably not. HD800s or SR009 are probably the very best headphones, but nothing is going to be that much of an improvement for competitive gaming over the AD700s.
Your NOT going to keep getting competitive improvements as you go up in price. The main improvements your going to get are a more immersive sound (fuller weighter sound, better bass). Sometimes a more immersive sound counteracts a competitive focused sound though. Part of the reason the AD700 works so well for soundwhoring is because it sounds bright and bass light (counteracts immersion though).
So if your looking for the very best headphone for competitve gaming, just get an AD700. Or get an HD800. Everything in between the two will offer improvements to immersion, but not really improvements for simple competitive sound whoring. If your willing to trade a little competitive ability for a more immersive and enjoyable sound (and a more audiophile headphone that will be better with music), then you should look at more immersive headphones.
[*] What traits make for a good competitive gaming headphone?
A non-bassy heavy signature, emphasis on mids and highs to bring out details like footsteps, and a large and accurate sounding soundstage...
[*] What traits make for a good immersive gaming headphone?
[*] What' the difference between "Dolby Digital" and "Dolby Headphone"?
Dolby Digital surround and Dolby Headphone surround are NOT the same thing.
Dolby Digital is a compressed and encoded 5.1 channel signal which can ONLY be passed through optical or HDMI. Dolby Digital is actual surround sound (5.1 channel), NOT virtual surround sound for headphones (2 channel). You can't listen to Dolby Digital with headphones, unless your headphone has multiple drivers. To get virtual surround for your headphones you need to process that 5.1 channel into a 2 channel (stereo) signal that your stereo headphones can actually use. That's where Dolby Headphone comes in.
Dolby Headphone is a virtual surround sound DSP for headphones which takes a Dolby Digital 5.1 channel signal and downmixes and processes into a special 2 channel stereo signal that any headphone can use. Since it's just a 2 channel stereo signal, any 3.5mm jack will output it and it will work with any regular stereo headphone (although some work better than others). Even though it's only a stereo signal, it still sounds like surround sound when used with headphones because the Dolby Headphone DSP adds head related transfer function cues to the signal, which fool the brain into the hearing the same surround sound that was in the original 5.1 signal.
[*] What's the difference between Pro Logic II and Dolby Headphone?/What is Pro Logic II?
Pro Logic II is basically a 2 channel signal upconverted to interpolated mutli-channel surround, while Dolby Headphone is basically multi-channel surround down-converted to 2 channel stereo with virtual surround from added HRTF cues.