I tend to default towards legato in Bach, as my main place of playing is so "dead" acoustically that staccato sounds, well - silly for want of a better description! I find - rightly or wrongly -that my personal preference is for an almost Dupre-like legato for many chorale preludes (eg "O Mensch bewein", "Nun komm, der heiden Heiland" and "Liebster Jesu")