Let's not consider color or fabric: let us just consider the fit of the pant.
The waist should be comfortable, but you don't want it too loose. You don't want the pants to sag below your cheek line, or, if wearing a belt, you don't want the material to be pinched and folded by the belt. You also don't want the waist to be too tight. Like I said: the waist should be comfortable and fit just right. The crotch and buttocks area should also fit just right -- not too much fabric and room, but not too tight, either.
As we move downwards, it's here where good men can begin to differ. There is a range that can work. Perhaps a slightly roomier, straight leg cut, but not too roomy. Perhaps something a little sleeker and closer form? Perhaps a slight taper? Yes, perhaps. But there is a range: too roomy in the thigh or moving down towards the break, and it won't work. Too tight, and it won't work. And speaking of break, there is also a range that can work for the length of your pant. But too short and you have a problem, or too long and you have a problem.
All of these questions I've been considering in a vaccum, not accounting for body type. Body type matters: within these various acceptable ranges, certain moves in one direction may better complement a certain body type more. But even considering body type, there is still a range that can work for that particular body type, a little roomier or a little slimmer.
Once you've found your range, do you need to pick your particular cut within that range and stick with it across all your pants? Or can you wear a pant that is on the roomier end of your spectrum one day, and then switch to a pant that is on the slimmer end of your spectrum the other day? It's this question which no one has yet satisfactorily answered.