As I breastfeed Dominic and have no use for this contraption, I really cannot offer much advice. In any case, I don’t think there is a lot of ‘science’ in this. Just get anything you fancy, taking into account ease of use, and capacity. As your baby grows, he will be taking larger amount of formula and you want the individual compartment to be big enough for each serving.
Also, take note of the number of compartments. Depending on your lifestyle, you may not need to buy one with many many compartments – these usually come in the stacked-up version which I personally find not as user-friendly. I actually do own one. It’s a round container, divided up like a pie chart for the individual compartments. To pour out the content, just twist the cover so that the opening is over one filled compartment, open the opening and pour.
If you are not using this container for formula milk, the good news is that it can double up as a snack container later on for small snacks like raisins and cereal for your baby.