I've smoked white rhino(nirvana) and it was good and very strong. But if you mean what has the best cerebral chatty high, then I'd say Super Silver haze or some other strong hybrid. I don't grow indoors, so I don't know from experience but my friend gave me super silver haze and it was very strong. That shit made me talkative and then had me crawling. From what my growing friend told me sativa dom strains tend to be very strong, but more problematic to grow.

To be perfectly honest with you, there is no defacto "strongest strain" of weed. From the weed I buy, I could tell that I payed a lot of money from some overhyped stuff that tasted earthy and grassy and wasn't cured properly. All these strains are bred for potency and if you grow them right and select a nice phenotype you too could have a power plant.