I can say the 4.2 is a tough motor. I use one in my NRCS work truck, a 99 F150, 205 horse. The radiator has been plugged with corn stalks, crop residue, etc. and overheated the motor to the point where it boiled over. Not realizing it was that bad, I drove it back to the office, where I refilled the radiator, and all was fine. I did this not once, but several times. There was very little coolant left in the motor.

I couldn't find any obvious clogs despite looking, which is the reason I did it three or four times. Finally sent it back to the dealer, where they took off the skirt, finding all kinds of crud up there.

It's an adequate motor for the F150, and it will scoot if you bury your gas pedal all the way to the floor, but as a truck engine, it's not as good as the 300 c.i. inline six it replaced. My reasoning:

1) Mileage has consistently averaged between 12.8 and 14, and that's nearly all (90-95%) open road driving. My 300's beat that. Best the 4.2 ever did was 15 mpg, at 55 mph. 75 mph really sucks fuel.
2) It doesn't have very good low speed torque, and must downshift to do EVERYTHING. This despite fairly low gearing in my diff. Low speed torque is sacrificed so the V6 engine can generate impressive horsepower numbers, which actually make it less suitable for a truck. It must rev twice as high to put out comparable torque to the inline six. (EFI 300-265 lb/ft @ 2000 rpm, 4.2 V6 250-255 lb/ft at 3800 rpm). Despite a considerable breathng handicap, the inline made more torque, especially in the practical sense. A 3800 rpm torque peak is unavailable, or undesirable, in a towing motor, especially one of modest displacement. At clutch engagement engine speeds of around 1000 rpm, it's no contest. The 300 puts out way more than the 4.2, which is why it's considered a stump puller.
3) The inline's flat torque curve vs. the V6's much more peaked curve. At towing speeds, you're right in the 300's powerband, with full peak torque available. With the V6 you're 1500-1800 rpm below peak torque, on a sharply sloped curve. Result? When you hit hills pulling a load, the V6 downshifts sooner, and revs like mad. Doing this occasionally is not a big deal, but gets really annoying after your fifth hill. Revving engines build up a lot of heat, too, not good. High revs, frequently=bad things when towing.

For a full time puller, gimme the 300 every time. Both motors are better with stick shifts, but both models were stuck with light trannies, the 300 at the end of its production, and the 4.2 as currently produced. That's why my harder working 300 (of the two I own) has a T18. Both the 300 inline and 4.2 V6 COULD be rated to tow approximately the same load, but the bigger displacement, lower revviing inline is a lot more satisfactory, and will last longer while doing so.

Its weakness was that it was so gagged for breathing during its production that it was around 25-50 hp and 50-90 lb ft below its potential. This could be obtained with a better exhaust and intake, which could have easily been done. No fancy mods or high revs needed, and it would still retain the low speed torque (this would increase too). Still, it's hard to sell a lower hp engine these days, which is why a 205 hp V6 seems to be more attractive as a motor (230+hp soon!), and seems to represent progress, as hp is all most people know about.

Where the engine makes its power is more important.

If'n you wanna race though, the I6 will not keep up with the V6. Revving motors win races. The suitability of the motor for a given application depends upon how you want to use it, and the jobs you are asking it to do.

Which is why some prefer one type over another.