Can't go wrong with big-bud.
I think you may have some THC percentages mixed up.
G-13 can run the gambit between 8 and 18 %
Highest official THC is 23.5% by White Russian (White Window x AK-47)
THC is more about grow conditions than actual strain, although genetics does matter a lot.(UNARGUABLE)!
Ugh, don't get me started on all the misconceptions of G-13.
Clone-only?(perhaps)
Government-developed? (NOPE NOPE NOPE!)
Whatever a dealer calls good headies he gets? (probably)
Anywho, I'd recommend Big Bud, White Widow, AK-47, or any other commercial indica for you, less finicky than sativas and big dense(or loose depending on light) heavy sparkling nuggs if grown right.
And any of those names will command a high "commercial value"(I in no way endorse you selling them, of course
), with the exception being big bud.