I have worked for AutoZone for 2.5 years now and have learned alot about plugs.
The #1 rule is: Stay with OE plugs...you can never go wrong with OE!
Bosch plugs are pretty much only for German cars. Kinda like the Densos are for Japenese cars.
I sell a lot of Bosch plugs at work. The Fords do ok with Bosch from the comments that I get from customers. Ford cars arent as picky as say GM. Dont even think of using Bosch in a newer GM (because of the ignition system).
I run Motorcraft in my Bird, if i try any other plug, it will be NGK iridium or V-power.
NGKs are awesome. I have yet to hear one bad comment on any NGK plug. I had Bosch, Denso and then NGKs on my old Accord. The NGKs are great!
I'm not bashing any manufacturer. Just stating some facts and opinions. And my 2 cents...maybe 3.
1991 Ford Mustang GT
1998 Lincoln Continental
1999 Mercury Mountaineer 5.0