It's a good thing you asked this question here and not on a truck board...I've seen some nasty fights develop over the advantages and disadvantages between a straight-6 and a V-8.
It is generally believed that an inline engine will produce more low-end torque than a similar-sized V-engine, but that a V-engine will provide more high-end torque than the inline engine. I actually prefer inline engines for their simplicity (an inline-6 typically has 40% fewer moving parts than a V-8), and I have yet to hear of an inline diesel engine breaking a crankshaft (except for some guy in a truck tractor who abused his engine, but it still got to the shop running on the aftmost 3 cylinders!).
