Someone else, (with more amp experience than me), can comment on the sonic side of this question, but from a strictly electrical point of view, I'ld prefer 16 ohms for two reasons.
16 ohms means lower current. Lower current equates to less heat.
Also, if you want to add a second cab later, in parallel, it drops you to 8 ohms, which is still a nice middle-of-the-road number.
Just my 2-ohms worth.