By weight? I'd say that it most certainly is stronger. An extract means that the sought-after ingredients are extracted from, in this case, the root and most likely the resulting solution is concentrated or evaporated completely resulting in pure product. I'm just going to throw around random numbers, but for example 1g of dry root contains 60mg of active compounds; with a theoretical 100% extraction efficacy you can get 60mg of product in solution, which you can evaporate, which in turn will leave you with 60mg of solid product. So that would be stronger by weight, but also would probably mean better absorption etc. Extracts are stronger as a rule, otherwise there would be practically no point in making those at all.
That aside, I've tried both making tea from the root and popping extract pills. Only the latter has ever proven itself to be somewhat effective in inducing sleep, apart from that I think Valerian root is extremely mild overall.
