Please do not base your choice of strain on THC percentages. The high you experience is a direct result of the unique cocktail of cannabinoids in each strain.
There are at least 66 different cannabinoids present in the resin heads, only 3 of which we can measure . This unique recipe is incomplete if even one ingredient is missing, and this is in large part a result of the environment and inputs you (the grower) provide.
As far as BC seeds, I acquired ( from GC3), a Elephant Bud clone, where BC says its the strongest Bud in the WORLD! according to them 26% to 34% Thc, well i dont know bout that, but it IS a great strain.The taste, high, and yield are right up there with some of the best I've experienced.