Sleeve length, yes, but tightness also
The length of your shirt sleeves is important. At the correct length, they display the slightest strip of linen peeking out at the bottom of your suit sleeves, defining the colours and the shape of each. It is a key locus of style, the display of the deliberate relationship between wool, cotton and leather watch strap.
So let’s review the guidelines on length. The suit jacket should fall to your wrist bone; the shirt should fall a little lower, to the base of your thumb. The difference is that quarter to three-quarters of an inch in peeking linen.
One important thing to note about the length of the shirt sleeve: that point at the base of your thumb is also the narrowest point of your hand. So, if the cuff is tight enough, it will stop at that point anyway. It can go no further down the hand.
This does not mean that your cuffs should be super tight. Neither does it mean that their length is irrelevant. But it does mean that both length and tightness are important.
There is supposed to be some slight bunching of shirt material, some excess, at the end of your sleeve when it is by your side. It should not be the precise length of your arm up to that point. This is so that when the arm is extended, the cuff does not come up short, held up by its shortness of length. Rather it has a little excess to go with the arm and stretch out.
This excess length should not be too great – no more than half an inch to an inch. And the cuff should not be too tight – snug without being constricting, allowing for a watch or any other jewellery with a small amount of room for comfort.
So the cuff should not be wide enough, for example, for you to slip your hand through it when it is fastened. A French, double cuff will always be larger than a barrel, single cuff of course. But neither should allow for you to push your arm easily through.
I do not disagree with Will at A Suitable Wardrobe very often. His sense of colour in socks and shoes, for example, is consistently inspiring. But I do feel he is wrong in writing here that intricate cufflinks should be attached before a man puts a shirt on. If that were the case, there would be no room for a little excess material in the shirt sleeve and it would always stop up short when the arm is extended.
The length of your shirt sleeve is important. But the tightness is, also.