Incorrect: the anti-drainback valve is designed to prevent "unfiltered" oil from draining back into the crankcase, possibly taking even more dirt off the filter. Most good filters will have two sorts of valves- the pressure relief valve which is designed to open up if the filter becomes too clogged with dirt to allow proper flow, and the anti-drainback valve. If you have removed a filter off of a filter mount that is upside down, you can see the result as the filter will be mostly empty: only enough oil to saturate the media (perhaps 10-20% of total capacity) will be left.

That said, you imply that its better to have a full filter at startup to prevent the momentary period where there is little or no oil flowing from the filter- I agree, and I think in general upside-down filters are a bad idea: I really do not understand why they have been adopted as the only benefit (to me) is its slightly easier to remove. I wish somebody could explain why Merc adopted the upside down filters mounts. Maybe they took less space? Maybe $5 cheaper to manufacture ?

What would you recommend for a stock 496 h.o. Running stock mercruiser filter now, and Valvoline VR1 20-50, from what I have read I am in the right direction with the oil, the more I read about the filters my curiosity has gone up.

My preference is the Amsoil filters, but I also use Purolator Pure 1. that's pretty much all I use on my boats. For cars and trucks I also like the Wix, Mobil 1. Like some of the oil filter studies you find online, I too have disassembled new and used filters to study what is inside them. Some are really good, some are crap, most fall in between. I too dislike anything Fram, and since a ton of counterfeit Chinese Fram filters entered the USA it has further depressed an already weak reputation of Fram products. I don't know who actually makes the Valvoline labeled filters and have never run across them in a study, so I cannot comment on them. The stock Merc filter certainly would be sufficient. Most likely you would need a Amsoil EaO24 filter but I would check an application guide. Let me know exactly what year, engine etc. and I can probably get you a number of alternatives besides Amsoil.

Doesn't Wix make the purolater? I think they do.

I run Wix Racing with Mobil 1 v twin on my 496HOs

Those filters DO have the anti-drain back valve.