Each to their own and whatever works for you MM. I don't have much time for sectional times though I know successful punters who do. All the races I've seen were won by the horse that went the fastest from the starting gate to the finish line. As to the other factors you mention, I consider them wind noise. A multitude of variables can affect race times of course but I would argue they can all be accounted for by the difference between expected time and actual time, although variables such as tempo mean that a single race is not necessarily a good arbiter of that.