[glassdoctor]

From a practical standpoint, one might be better just based on how you could use the packs, as starscream said.

Electrically it makes no difference... all three examples do exaclty the same thing.... EXCEPT... that example "b" doesn't have the advantage of having the cells paired up in "2p" sets. This essentially makes each set of 2 cells into a single cell that will balance itself.

(This assumes that in example "c", it's built in a standard method by first making 4 sets of 2 cells in parallel, then running those 4 sets in series.)

In example "b"... you have twice the odds of a cell going out of balance because you have 8 individual cells rather than the effective 4 cells in examples "a" and "c".

The other guys have already said the same thing, in other words.

Having said all that, I like the flexibility of having two 4s 4000mah packs if you have a use for them. But then, I built mine as a single 4s 8000mah pack. lol