S-pouches fell out of favor because they are prone to structural/functional problems. Sometimes they are still done when there are intraoperative issues of a too short mesenteric reach.
W-pouches are OK fr the most part, but have an increased risk of an overstetched pouch hat is difficult to empty.
Bottom line though, while S and W pouches have a short term increased pouch capacity' in the long term they do not fare better. So, since the long term result is the same, it makes sense to do the simpler procedure.
Still, various surgeons have their preferences.
Jan