Matter of taste. The Cubed Baby requires you to own Poser, because it is based on the P4 Baby.  (You need RTE to decode the Files for the Figures) Support is limited for both, but there is a lot of stuff for the old P4 Baby that might work on the Cubed Baby.

I also think the Cubed Babies are more Newborn to 6 months and the Mil Baby is from the latter to Toddler. They both might have a place in your Runtime. There are also two versions of the Mil Baby.. the Mil Baby 3 is the newer one and the better one, but there is support for the older Mil Baby.

ratscloset
aka John