I asked Jean Jacques this same question. Suggest mostly right before training, this way your Jiu Jitsu is at its 100%, and you strength is train. Says something like "everybody whos fresh has good jiu jitsu, then when they are tired, the real talents show themselves." not word for word, but something like that.
Ive beed doing it here and there, its hard to push yourself mentally, but ive never once regretted lifting weights after. Do both, but to test your real jiu jitsu and your ego, do it before training.