Fireman Dave summed it up pretty good
I had a '98 4x4 QC Auto, and now I have the '01. 5 ETH. In my case, the new truck has better brakes, and more power. The fuel filter is easier to change, and the "one touch" power windows are nice. I also prefer the standard transmision over the auto. I pulled a small travel trailer with both trucks. I have checked mileage on both trucks for every tank burned. The 24V and the 12V got the exact same mileage on almost the identical trip(pulling the trailer). The 24V did the trip faster and climbed the mountains faster than the 12V auto. In my case, the mileage empty is slightly better with the 24V, but not by very much. The 12V engine was quieter in the cab compared to the 24V, and seemed smoother overall compared to the 24V. My '98 also had a better "fit and finish" than the '01. 5. If I could do it over, I would have probably kept the '98 and looked for a wrecked donor truck to do a standard transmission conversion. If I had ordered the '98 with a standard transmission, I'd still have it.
I have come to the conclusion that I will keep this truck for a long time. If the VP 44 craps out of warranty, it will either get a Bosch P7100 pump, or a 12V engine that has one on it.
If I were in your shoes, I'd keep what I have and bomb it.