I think the thing is, Emotions, that I can see the sense of both scenarios (though favour dark-creeping myself). So it all really depends on what Oscar and Reeva usually did.
Although... this is somewhere else where I struggle with Pistorius' testimony. Just minutes before, he claimed the room was black as pitch - so dark he couldn't reliable see Reeva in the bed a few feet away.
He then got his gun, and proceeded to where he thought the sound came from. In pitch dark. Now, I can see why he didn't want the intruder to see him, but at that point, he's got a wall between him and them, they've got a clear get out route (the window) and by leaving it pitch black, he runs the risk of them stumbling over each other in the dark. That strikes me as being particularly dangerous.
My 'leave the lights off' scenario works in my house because there's a fair amount of ambient light. I can see a shape in a room, and I'd put the light levels at 'murky'. And I still occasionally walk into the doorframe. His was utterly pitch black, because he couldn't see Reeva.
The other thing I wonder about, in a pure conjecture way, because I don't know, is whether the bullet pattern suggests that there was more light than he's letting on. I've never shot a gun in my life, but I can imagine in a situation where you knew there was someone somewhere, but couldn't see enough to be sure, wouldn't you shoot over a wider area? His four bullet holes are quite tightly together.
So then were at a point where it was so desperately pitch black that he couldn't see Reeva from a few feet away, but there was enough light in the bathroom for him to know for sure where the toilet door was, without any guessing or honing in or needing to adjust his angle at all.
I'm not saying that's impossible - he might have been way better at room layouts than me, and might have better sound location and all that. I'm just saying, in my head, when I imagine it, I always imagine a murky light at that point - not pitch darkness.