Being a mechanic at a ford dealership i saw the engine guy replace quite a few of the V-10 3 valve engines they also have a problem like the 5.4 3V to shoot spark plugs out of the head destroying the COP and needing a helicoil insert.
i would personally prefer a 2 valve V10 ive owned 1 of each of the 2 valves *4.6 5.4 and 6.8* and never had any issues with them.
As he said these are high RPM motors let them spin my F150 did not make max HP and Torque till 4300 + RPM!!!.
Keep up on oil changes these engines need oil changed regularly due to the over head cam design.
Friend had a 6.8L excursion and it would get between 6MPG **towing 10K** to 10 MPG *Unloaded*
The exhaust manifolds seem to be a real issue too and can get really costly quick. Not nearly as many V-10 parts out there as 5.4 parts.
Good luck!!