Hi alpharalpha,
As long as you had proper center reinforcement of your slats to avoid sagging, I would have you lean toward the slat system, as this would allow for better air circulation around your mattress.
A two sided mattress that is rotated and flipped on a regular basis (see post #2 here) will certainly last longer than a one sided mattress that uses the same comfort layers on only one side of the innerspring (even with very durable materials such as latex) because for half the time the comfort layers on the bottom of the mattress aren’t subject to the same amount of compression forces that soften and break down the materials over time as the upper layers in the mattress. There is more about the pros and cons of one sided vs two sided mattresses in post #3 here and the posts it links to.
I can’t comment upon the pricing but if you want to make the product two-sided and increase your durability it doesn’t seem to me to be too large of an extra price to pay.
I’m interested to hear how your “experiment” turns out.
Phoenix