I would pick the Manson for many reasons but the real difference is its ability to grab the bottom. The delta plows the bottom which opens up the surface of the bottom. The Manson Supreme and Rocna both compress the surface which translates into better holding power.
Imagine a "V" shaped snow plow. It pushes snow to the sides. Now redesign that plow into a "U" shape with the open end in front. That plow will not go far.
And I am on 2 forums that Craig will frequent and have never seen him get obnoxious. Regardless, he produces a great anchor.
With all due respect, I don't think these plausibly-sounding analogies (snow plow) make a lot of sense. Just one example: the snow plow rests on a hard surface when you pull it, the anchor does not (except when there is a layer of rock under it, in which case it becomes a question of rolling your dice with any anchor). All anchors are designed to bury INTO the substrate, not slide on it, which is exactly the opposite of a snow plow, you definitely don't want to bury that into the road.
I have seen a Delta anchor completely buried deep into the sand, only the chain sticking out, after a few days of storm. I am sure that a Manson (Bugel, Wasi, Spade, ..., even a Rocna) would do the same, this is where an anchor gets the serious holding power. In this situation, the question is which one gets buried faster and deeper, and I don't think we can answer this by arm chair anchoring.
Oh, and Craig never "produced" anything (other than hot air, and that one foul-smelling). If you look at the AS link I posted, you will seen that his so-called affiliation with Rocna was very tenuous at best, and that the company does its utmost to make that clear.