We haven’t tried the specific ones you’re asking about, but we have tried cylinder head replacement kits (for repairing multiduct gasket coolant leaks). We bought 7 from Global Marine Power earlier this year. So far 5 of them leaked and had to be replaced after about 6 months. Everything in the kit looked and worked good except for the red sealant around the coolant port on the multiduct gasket. The red sealant was paper thin, where Wartsila’s is very thick. I wouldn’t be nervous about using their products for side cover and valve cover gaskets though. They are much less expensive.
We have had success for several items by going to the vendor directly. One example is the HT/LT Heat Exchanger Water Pump Mechanical Seals. We had significant issues with leaking and found that the installed seals were not Nitrate resistant. We talked with the vendor and they made the Nitrate resistant seals and would sell direct. We have also speced out several O Rings and had them made locally.