DeWalt dcd999 FlexVolt

Hi! I am thinking of buying the dcd999 that has FlexVolt capabilities. But I’m not sure I will buy the 6ah FlexVolt battery. Will it make a BIG difference if I use a 6ah FlexVolt compared to a 5ah 18v battery? I know DeWalt claims 42% increase in power with the FlexVolt, but is the difference really that big? And is it really necessary to get the $160 FlexVolt battery?

I still own the 996 and have had it for several years. I smoked it once while drilling with a large auger bit but the drill still works strong last summer.  If you look at the Dewalt site they say 42% more power with a 6ah flex volt over the 5. Having said that, I was using the 5 and was placing several 3/4” rebar pins into double stacked PT 4x (old lumber) for two retaining walls. The 996 minus the last smoke show with the 5 did admirably. I beat the crap out of that drill. Everything I’ve heard about the new Dewalt advantage and the power detect seems to indicate they made some significant advantages in the quality of the tool. That being said I drilled about 20 of these with a 5 and she still works great (I spent last week drilling plumbing and wiring holes into sub floor and stud) so I am pretty sure the 5 will still be enough power unless you are doing some really really heavy duty drilling. Generally speaking now I use the new larger packs as I sold my last 5 and have been using the new high capacity 6, 8 and 10. I switched most of my outdoor tools to cordless and use Flexvolts in those except my lawn mower which I use the 10 and that thing goes like a beast.