In a full ring game (8-10 players), 72 offsuit is the worst hand, because it contains the lowest two cards you can have where you can’t make a straight or flush using both cards. In a headsup match, 32 offsuit is the worst hand.

What causes the difference?

The higher card strength with the 7 plays better HU, and the 23 plays better at hitting straights at a full table. Like if you hit a pair with 23 HU, it’s more likely to get outdraw on than 27 will if you hit your 7.