Heads up, or full ring? In a full ring, 27 is worse since one pair will almost never win it, while two pair or better will win or lose regardless of whether it is 27 or 23. A straight will win a sizeable percentage of the time, which obviously favors the 23. Heads up, high card wins a reasonable amount of time, so 27 would be preferable to 23, although still far from a good hand.