Matt, I can describe it in quite some detail, as I've owned and extensively used both Hot Rails and Joe Barden Strat Deluxe neck pickups.
I was a hardcore rail pickup advocate until a couple of months ago, when I installed the Irish Tour.
I would say that the main difference that you get with a true single coil is what I would call focus: there is a pinpoint precision to the notes that you can't get when you sample the string in two places, which is essentially what a rail pup does (as well as mini-buckers), even tho they are very close together.
The noise was always a factor to me with a single coil, but I was amazed at how quiet a scatterwound pup is compared to a machine wound. The reason, according to Tim, is because a scatterwound pup doesn't form the same 'lumps' in capacitance which plague a machine-wound pup. (I hope I'm getting that correct)
Now, before you think that it's all attack, I can also say that the neck SC has a sweetness that you can't get with rail pup; rail pups are what I would call an imitation single coil sound; they attempt to mimic the tone, but without the noise.
I can describe it like this: modern movies can depict vast armies and other eye-popping delights via CGI; however you never fully suspend disbelief. Image that with guitar tone now: a rail pup is like a CGI single coil pup: you get all that quiet and an amost believeable single coil imitation.
Personally, I'll take the models from Empire Strikes Back any day over the computer-generated ships from Episode III.
Hope you find that helpful, or at least coherent! LOL
As for the Dave Murray question: This is the tone I wish Murray would have!! He's 1/2 way there, now that he's using Wayne guitars, but he needs to complete the circuit! (To use another Star Wars reference)
