Well lipo cells vary a minute amount in energy density depending on the mah, and shape of the cell... so, it could very well be that one way might be a little lighter than the other (2p vs. a larger 1p), but I don't know which is the best way. Also, if you have to do more wiring, that will add mass as well, and connectors. Who knows?
“The modern astrophysical concept that ascribes the sun’s energy to thermonuclear reactions deep in the solar interior is contradicted by nearly every observable aspect of the sun.” —Ralph E. Juergens