idi vs. isuzu npr

[tnmtn]

i have been running a '94 350 cclb in my signature. the engine isn't turbo'ed. Although it is running like a top now with new IP and lift pump and timing being reset i am thinking about another truck to take some of it's workload. I like the Isuzu cabovers and they seem to have similar HP and torque numbers when compared to the idi but also have a higher rear end ratio. Could someone explain why one of these wouldn't tow at least as well as the idi?