Do you think they are comparable with flow rates? Which one would you use if flow rates mean alot to you? I have been using the K&N for three years now and have been impressed but I have a new Mercury Racing filer that i would like to use thats been sitting in my cabinet for a 3 years and it cost quite a bit so it would be a shame not to use it. The motor is a 6.2 mercruiser that i would be using this filter on.

The Merc filter will be just fine. Its the same filter that would get put on Merc engines making more than twice your hp at a dealer.
Oil Filter Update

Used the K&N, Mobile 1, and Wix standard one for years. All seemed well constructed, no issues. But then again you normally dont see issues very often.
But there could be a problem and you never know it. There are some cheap built ones.

I've used F... most of my life until about a dozen years ago. they started getting so cheaply made. At least the standard ones. Two of them at different times had problems. The pleats came apart where the glue was at the ends. i could see it was a terrible glue job. I returned the bad ones, the company sent me a half dozen back. Cut one open - never used them since.