Historically inlines (where all cylinders are in a row, and in the same head) tend to last longer and wear better. If you look back at engines that were considered to be "bullet-proof" you'll see a majority of them were like his.

V- Engines, where the cylinders are split and handled by more than one head tend to have more wear issues and *not* be as bullet-proof.

Naturally there are exceptions to everything, but this tends to be "rule" in this case.

The key word in all this is "historically".

Pete