Dan -
Hard to beat the OEM Motorcraft plugs that are specified for your 5.0. That's what I'd recommend. Using anything else is just wishful thinking that they'll somehow improve performance over stock. They won't.
I'd have to back up your opinion of Bosch plugs. A few years back, I had a coupon for a good deal on a set of +4 Platinums, so I figured, what the heck, I'll try them. Worst plug I ever used! About 3 or 4 months later, my motor started missing under acceleration. Long story short, it was the +4's. Two of the insulators were cracked, and on most of the plugs, the electrodes were out of alignment. Since they have 3 more electrodes per plug, that's 3 more chances that the gap on those will be wrong. Anyway, I installed a fresh set of stock Motorcraft plugs and, voila, no missing, the motor was back to normal.
As for platinum plugs in general, platinum is less suseptable to corrosion than copper is, which means it should last longer. But copper is a better conductor of electricity than platinum is. How many race cars do you know of that use platinum plugs? I don't know of any. Winston cup, NHRA, IRL, CART, F1, Outlaws -- none of them use platinum plugs. They use copper plugs. They're looking for performance, not longevity.
