Having the saddle tooooo loooooow, maks for really hard pedalling.......

If you like to ride in a more cramped up position, get the smaller - if you like to ride more stretched out, get the larger.

When seated on the bike, you should be able to put your heel on the pedal, and pedal backwards, gaining FULL leg extension, without rocking n the seat. Then, when you pedal normally, with the ball of your foot, you have a slight bend in your knee.

When you stand over the bike, and you can pick up the front wheel off the ground, the bike is not too big - but a too long top bar will have you out of position, unless you like to ride stretched out.

At your height, I'd get the larger, especially in an upright bike.