The easy part of that decision is knowing capacity you need to survive between wall sockets.
It's straight math of take your device's known battery life and how much more life you need and use the 3/2 rule. e.g. your phone lasts 6 hours, you want to last 18 hours, so you need 2x your phone, your phone has 3000mAh so you need 6000mAh, so use 3/2 rule so you need 9000mAh, and so a 10000mAh is enough.
The hard part is know how long you have to recharge. If you are using the above to last til bedtime overnight access to wall socket you need just to recharge in 8+ hours. The main difference in cost between the Anker products is that recharge time.
Because output Wattage of a Powercore is easier to be higher than the input wattage of a Powercore, Anker headlines, promotes, calls out primarily, the output wattage but that is actually in real life not that critical, as a portable charge can always be just connected longer. The harder part is the recharge input wattage, time to recharge a Powercore. That is harder and also more important, as for example you can easily buy a Powercore which lasts all day but takes too long to recharge than you have.
Once you know your recharge situation then you can compute the charger's required specifications, e.g. the above example of phone + 10000, 13000mAh @ 3.7V = 48Wh, then use 3/2 rule, your recharge time (8 hours) means 48*3/2/8= 9W minimum charger.
We have discussed in the past that Anker needs, like APC does, a calculator, to input your devices, and your context (e.g. overnight recharge) and it recommends products to match. Anker never did that, in part as their products are too diverse, too many products, too many variables and documentation is patchy.