John and Air Rabbit are spot on and correct; like in all segments of life there is some educated people; who learned the ins and outs of all the problematics; well outside the box of REQUIRED knowledge.
And this is where the problem lies within this discussion. For most of the pilots being trained , there is only one V1, the one given on that take off, on that day on that condition, for a balanced field condition, most of the time; and FMC/performance programs etc are giving this exact number with more or less 100% accuracy ( if the data are entered correctly by the crew). BUT, and there is a BUT. This specific V1 presented was chosen from the performance charts by the operator from the manufacturer after certification; this process is totally opaque for nearly 100% of the crews flying the plane, they just have to stick to the said numbers, the rest is the test pilot world and has NOTHING to compare to a day to day ops.
For the rest, and no contest here, since it is not the same league at all; please speak among yourselves at the bar, bitching on whoever you want, ppruners, Chief Pilot, other idiots in the field; but just do you job : STICK TO THE MANUAL, and FLY the NUMBERS!! This is what you are paid for...( Hopefully)