I don't think he's talking about Denkall's T-400. He said they were both BDL. BDL has a 400 mg Test blend:
90MG PROP
60MG PHENYLPROP
60MG ISOCAPROATE
60MG DECANOATE
65MG CYP
65MG ENANTH
I really don't know what the advantage over straight Enanthate or Sustanon would be here. One of my freinds is just about to start on BDL's 250 mg Test blend (200 mg Enanthate, 50 mg Propionate). A little simpler that Sustanon (sust), alot simpler than BDL's 400 Test blend.
I guess it depends on your cycle history also. If this is your first cycle, I'd say go with straight Enathate. If your a little more advanced, and your adding a few other things and want to experiment a little, try the blend.