I'm curious how 5ah in one battery equates to more in a different 5ah battery? 5ah is 5ah no matter how you look at it? Seems like a lot of marketing BS to me? I also haven't seen any data showing that pouch style cells have better "output" than typical 18650 cells. Now, they could be using a higher quality cell, or higher quality construction that could net a bit higher output.
I am guessing this is still involving a high amount of BS and marketing magic.
Different battery chemistries have different characteristics. Within the typical moniker "Lithium Ion" are (for example) lithium cobolt oxide and lithium manganese. The former have higher energy densities, so you get more capacity for a given size. The latter have higher allowable discharge rates so you can draw higher current from a smaller battery (and safely charge them faster). Meanwhile Lithium Iron Phosphate cells can recharge more times before their capacity is degraded.
Creating power tool batteries has always been about balancing the best size, weight, capacity, power delivery, recharge rate and life span. Choosing different Chemistries will indeed yield different performance charastice. Also, to date, we've been using existing cell formats (18650, 21700 etc.) and just creating packs based on stacks of these cells.
These new cells are lithium polymer cells which use dry solid electrolyte instead of a liquid electrolyte, which allows them to take different shapes than the typical dimensional cylinders. To that end, these cells have likely been created specifically by Dewalt for use in tool batteries which means Dewalt could also spec the chemistry to best suit the needs of power tools.
With all that said, it it completely reasonable to believe that these new purpose built batteries will be able to outperform the previous generation of batteries in the metrics that are important to tool users.
The best example I can give is voltage sag. When you draw power from batteries, the voltage drops. The more current you pull, the more the voltage drops. Let's say you have a li-ion pack that's measuring 21 volts hot off the charger. You slide it in your high output tool and pull the trigger, the voltage may sag down to 18 volts. Once you drain some capacity out of it, it's now measuring 18 volts under no load. Now when you pull the trigger, it sags down to 15 volts. Eventually, you get down to where the tool (or battery's) low voltage protection kicks in and shuts of the tool. You would say the battery is "dead".
The thing is, different battery chemistries are more or less susceptible to voltage sag. One may sag to 95% of the nominal voltage while another sags to 80% under the same load. So two batteries with the same "capacity" on the label (5 Amp Hours for example) may be able to deliver different amounts of "work" because one will trip the low voltage cut off sooner while the other keeps working.
