I've owned three modular motors.
1- 2 valve 5.4
1- 2 Valve 6.8
1- 2 valve 4.6 (current in a town car)
These are Great motors and have a relatively flat TQ curve which is ideal for what they are designed for.
My V10 was exceptional...the COP's can fail from time to time. The coil failure is strange because the miss will feel like someone is standing on the hood hitting the motor with a sledge hammer. It's not anything like a miss on my GM motors.
Never had a plug spit out in hundreds of thousands of miles driving and towing. And if it happens it is typically a few hundred to 500 depending on the shop and the damage. It's pretty rare to have to replace the head due to a spark plug spitting out.
I'm about to start searching for another Modular e350 Van or crew cab F350 SRW for my towing needs. V10 preferred but a 5.4 is a fine motor too for my trailer weights with the right rear end.
I have no interest in a diesel for my needs.
Thanks!
Jeremiah