Meguair's D151 or Meguair's M6601

[HardLineDetail]

I was looking at Meguair's D151 and at Meguair's M6601 and i'm wondering if they are the same or which one is better? I want to use it to use it on customer's cars. Do the wash and clay and finish with one of this two.

[KillaCam]

I never heard of M6601 until now. I'd like to know as well.
I have D151 and it's great for a one step! Not a bad price for a gallon either.