Re: how much faster is the 16x?
The theoretical, or maximum, answer is found by dividing 16 by 12 = 1/3 faster. The 12x TDK will burn a CD reliably in about 6.5 min. The 16x at best and in theory would burn one in 4.9 min.
However, as was said earlier, the actual increase in speed is much less. I also have seen the 50 sec faster statement. Both drives have burnproof. What that does is pause the burning process if the input isn't keeping up (because of other activity on the computer, or whatever), or otherwise going right. It is more likely to kick in at 16x. There is also the issue of whether the media can handle the burn speed. And 16x is brand new in all drives, and hasn't been tuned that much yet.
I decided that 12x was just off the bleeding edge, and the smarter buy, myself. Six months from now maybe 16x will be (at some point there will be physical limits, perhaps, at least at affordable prices). But even then 12x won't by that much slower. Now when they perfect a burning doing three TIMES the speed, like the jump from 4 to 12, THAT will be worth considering upgrading to. Burns in 2 minutes instead of 6.5.
Still, 6.5 for a FULL CD worth, WORKING IN THE BACKGROUND WHILE YOU ARE ON THE NET OR WHATEVER, isn't too shabby. You can burn 5 in a bit over a half an hour. Even for game trading addicts, that isn't too shabby. It's a while they're over there sort of thing, instead of an overnight project sort of thing for more than one or two.