Good fencers and boxers typically take a wide low stance. The boxer, Champ Thomas, was five foot eleven inches tall and stood with his toes approximately three feet apart [HTBAAWB] p.115. His feet were on a line through his partner and his back foot was about perpendicular to the line to his partner. His front foot was about 45 degrees to his front from the line to his partner. As in fencing Champ assumed this stance by stepping forward into the position. He stood very low with most of his weight on the rear foot. Many boxers point the front foot directly towards their partner. There is more than one philosophy of defense in boxing.
Aldo Nadi, who is considered the worlds greatest fencer, also used a wide low stance [OF] cover photo. Nadi has both feet pointed at about 45 degrees from the line through his partner with the front foot froward and the rear foot pointed towards the rear. This is not what is typically taught in fencing. Typical is front foot on the line and rear foot at 90 degrees as in Aikido. Wide and low is encouraged.
The basic Aikido stance is called hammi. The width is as if one is walking and freezes with the feet on the ground. For me this is 2.5 feet, which is a little narrow for someone my height, five foot eight inches. This is not quite as wide as boxers and fencers but it is close. In our club we tend to rotate our stance so that the front foot is pointed a little to our partners rear and the back foot is pointed slightly forward. This lets the torso more squarely face our partner, automatically moves us off the line of attack when we step and strike with the lead hand and it makes it easier to keep our hips under us rather than sticking out. Boxers typically move the foot to the partners back when stepping in to strike which also gets them off the line of attack. If one is to execute Aikido movements without bobbing up and down the hips must be kept low.
The basic Kuta stance is with the feet parallel and about shoulder width apart. This is essentially the same as the Judo and Jujitsu stance.