I have a Manson 35 and a Rocna 44 (20kg).

Pound for pound I think the Manson sets and holds better. I think it has the potential to set better in grass/weed/hardpack because it's blade is sharper and pointier. That said, the Rocna is no slouch. I use the Rocna as my primary just because it's larger and I think that is an overriding advantage. If I could fit a Manson 45 I'd sell my Rocna (it's a pre-China model made in Canada) but the Manson shank is higher (due to the extra stock above the stupid slot) and the 45 interferes with my sprit, while the Rocna 44 just barely fits.

If I needed to buy a new anchor today I'd take a good look at the Manson Boss. It's a lot of surface area per pound, pointy with a small fluke edge profile, and no hoop. Not only does the hoop interfere with a sprit, I think a hoop tends to ball up bottom material and can limit penetration depth. It's also a PITA to wash off a big wad of mud/weed when you pull it up.