see kai run shoe advice

the See Kair un website is havign a good sale. unfortanately for me, most are sold out in DD;s teen ybaby feet size.
I am debating buying her either of these two for next winter. she just got measure at a 20, which accordign to them is a 4. (keep in mind, shes 19 months. baby feet). she has been wearing shoes since sept/oct- she was a 19 then. so from oct till nwo, grew one size. would you get these shoes in a 5 or 6? or is this a bad idea altogether, buying shoes ahead?
I never bought SKR- how do they run?
also- which do you like better? they

for $23


or, for $21