One Battery vs Two batteries that Equal The Same Mah

Electric car battery packs are made this way with many sub units collected in a array of series and parallel packs to reach both current and voltage desired. I have a battery system for my solar array.  Here  I use batteries sets in parallel to be able to meet the current requirements. 

Take the DJI (sorry) Phantom 2 pack.  It is a Gens ace 3s lipo 5200mah; Internally it has 6 cells 3 series  sets of 2 cells in parallel.  Each cell is 2600mah giving a total capacity of 5200mah. It makes no difference whether this is done by wiring the sets internally or externally as separate batteries. 

While I agree that manufacturers blow up their claims and this can lead to sets not meeting specifications this does not change the basic rules that apply.

I also agree that more connections wire etc increases chances of failure but in the case of one or two batteries I think the chances are extremely low compared to other failure modes. I have never had a battery failure in the air but have had many other failure mode cause a ground intersect.Personally I am not arguing 1 versus 2. I see this as primarily a packaging issue space size COG etc.

My setup

11.1v 2200mah lipo, new and from the same manufacturer (not mismatched) AUW with batteries and camera is 2748 grams and she hovers at about 35-40% throttle (a little over powered I know and should probably be closer to 45-50%)

I get about 13-14 minutes of lazy to medium flying until I it 13.7 volts and bring her in. (it's a stable hexa camera rig, not set up for speed)

One should use batteries that are matched and in good shape. Same chemistry and discharge curves. In this case issue with unequal loading are relatively insignificant. If batteries of different type are used Martin note and not producing a pure additive current capacity would be true. But not with same chemistry / construction. The variation between cells is very low in good batteries.  Mixing a old used battery and new one can cause problems as well. Whether using a single battery with cells in series or batteries in parallel monitoring each battery cell and total pack health is a good idea to prevent in air failure. I do pack charge discharge curve on new packs looking at overall capacity and cell matching.  I do this periodically  ensuring the life of the battery to help ensure I do not have in use failure.  Typically with lipos I see single cell failures which is bad however wired up.