In reply to iksander:
I think the rectangle comment is a bit harsh; most well-cut jackets are a bit better tailored than that, using multiple, shaped panels.
I wouldn't let a suit tailor anywhere near an outdoor clothing item, as a suit a very, very poor basis for active clothing; the armscye, for instance, allows almost no arm raise, and arms must be held by one's side.
Any bespoke item should be better-fitting than an off-the-peg item, provided the method for converting body measurements to pattern blocks is good.
And, of course, we're all different shapes and sizes, so we really shouldn't expect every item from every manufacturer to fit us all perfectly.
Having said all that, the things that separate high-end manufacturers from mediocre manufacturers are the attention to detail, and the care taken with the design, and the evaluation and refinement of the design to ensure that all the features
work.