If you use the right filter element, the bypass filter will do a much better job of keeping the oil clean than a full-flow filter. I used to sell the Frantz filter system for big rigs that replaced the bypass filter cartridge on a LuberFiner 750 canister with one made of toilet tissue. It would trap particles down to 2/10 micron, (0.0002")
A full-flow filter can't restrict that much, because it would drop the oil pressure to virtually nothing.
The full-flow filter traps particles that could score bearings, and lets the small stuff pass through. Ideally, and engine should have both systems, but I don't know of any automobile or light truck engines that have that setup.
Jerry
For these reasons I believe the full flow conversion is overrated and unnecessary. After a Google search of "oil filter testing" I was stunned at how easily most filters will let dirty oil go by. I run an Amsoil bypass filter on my stovebolt and catch particles down to 2 microns absolute.
