I finally had some time to work on the comparison a little more today.
I picked up this Silver B yesterday, and decided it would be a good
one test these on.
I sprayed the Sam's on the left side of the firebox, and
the DPD on the right side.
If you notice in each corner, there are spots that are noticeably cleaner than
than the surrounding areas. That is where 30 minutes after spraying, I took
some steel wool and scrub for about 20 seconds. It total, I let the sparys do
their thing for 1 hour, then I took it to the carwash and gave it a good degreasing,
and power wash.
This is the DPD corner -
This is the Sam's cleaner corner-
Basically, no difference, and unfortunately, neither will prevent
me from breaking out the angle grinder and cup brush tomorrow
evening.

Final early review has me calling the competition a tie.
They both ended up similar results. However, I am calling in a victory
for the Sam's cleaner simply based on price. At $3 a bottle when bought
in the 3pack, vs $9 a bottle for the DPD when bought in the 6pack, it's
a no brainer. I highly recommend you get down to your local Sam's
club and stock up before the price on this stuff skyrockets the same way
the DPD has.
Speaking of the cup brush, I had to pick up another - I think my 4th
one in the past couple of months.
They sure don't last very long. I have been buying the cheapo's
at Harbor Freight. Are the better brands any better or do they
all wear down to nothing rather quickly?